In four months, adults in Colorado will be able to walk into a store, plunk down cash and leave with a drug that used to land people in prison.

No one, though, is sure what the future holds.

Will the new industry damage the state’s reputation, grow the drug culture, spread marijuana into neighboring states, intoxicate young people and spur more crime? Or will it bring an unrecognizable change, produce needed tax revenue, drive a stake in marijuana’s black market and extinguish unnecessary prosecutions?

“It’s like being sucked into a black hole. What is going to be on the other side? No one knows,” said Ry Prichard, part-owner of a hash oil company, TC Labs.

During the first week of January, when the first stores are expected to open in Denver, the world’s media will probably descend on Colorado to document the occasion.

Lines that form in the state for everything from new doughnut shops to ski sales are expected to wrap around businesses as customers queue up for the first buds.

“You are going to have the international media here for New Year’s Eve, and they are not coming for the fireworks,” said Denver City Councilman Charlie Brown. “Then there is going to be a photo that moves across the wire that is going to portray Denver one way or another. That is going to define Denver. It will be an image changer. There is no doubt.”

Rolling Stone magazine recently called Denver “America’s undisputed stoner capital” with two Jerry Garcia-themed bars, the same number of medical marijuana dispensaries as liquor stores and, of course, the Mile High nickname.

A grower told the magazine that the Platte River Valley running through the city has the highest concentration of marijuana on the planet.

“I remember the first day that I walked into a (dispensary), it blew my mind,” said Prichard, who takes professional photographs of marijuana. “Yeah, the shock of being able to see 100 edible products, 60 strains of marijuana, and being able to talk to someone who is knowledgeable about the product. It is going to welcome a lot of new people into the fold to understand how incredible and beautiful this plant is and how it has come so far from 30 years ago.”

Already businesses that cater to marijuana tourism are seeing an increase in interest — especially after last week’s announcement by the U.S. Department of Justice that the federal government won’t stand in the way of marijuana legalization in Colorado or Washington state.

Matt Brown, who started My 420 Tours in Denver, said he is getting e-mails and calls from around the world from people looking to come to Denver and experience the new industry.

“The demand has been ridiculous,” Brown said. “On our end, we have done zero advertising (and) made no attempt to seek media. But we are having hundreds of people a week hitting the site and people saying, ‘Please offer us some vacation packages.’ “

If everything goes as planned, stores will open during the first days of January — about six months ahead of Washington state, which also legalized adult-use pot last year.

Forbidden turns legal

Denver appears to be the only large Front Range community that will initially allow sales of recreational pot.

Glendale — a 369-acre town in the middle of southeast Denver — will probably see two of its three dispensaries convert to selling recreational pot in January. Glendale also doesn’t have a restriction against pot clubs, establishments that Denver has forbidden.

“We haven’t had any problems around the medical marijuana, and I don’t see that happening with retail,” said Chuck Line, deputy city manager of Glendale.

Other metro-area cities — Aurora, Littleton, Lakewood, Arvada, Erie, Wheat Ridge, Broomfield, Lyons, Longmont and Lafayette — have moratoriums. Boulder has proposed to delay business applications for retail marijuana until June. Louisville is still in discussions.

To prepare for conversion, Denver dispensaries are trying to follow every step of the new regulations that are still being finalized.

The city and county of Denver will grant retail licenses only to existing medical marijuana centers until 2016. The city also will require public hearings for every retail shop — a process that will create a tight timeline for the businesses to meet the Jan. 1 kickoff.

Hearings are expected to begin in November, after a 30-day notification period. Meanwhile, business owners are trying to get ready — growing as much weed as they can under the existing law.

New customer base

Andrew Boyens, owner of Natural Remedies dispensary in Lower Downtown, pored over statistics on a laptop in his fifth-floor dispensary one recent afternoon, trying to determine what his new customer base will be come January.

“We sit down all day long, trying to put together numbers and figure it out,” he said.

Rap music thumped from speakers in the small center, adorned with paintings of pop-culture icons such as Elvis Presley, Walter White of the TV series “Breaking Bad” and Frank Sinatra. Patients browsed, looking in glass jars filled with clumps of furry green pot.

Boyens figures at least 20 percent of Denver’s 13 million annual out-of-state tourists are pot smokers. He estimates at least 2 percent of those smokers — about 52,000 — will head to his shop for retail marijuana each year.

“If they all bought 7 grams, that would be 2 to 3 pounds a day,” he said. “That isn’t including Colorado residents. We think the demand is going to be through the roof. But we can’t be sure.”

Boyens said his shop must increase its volume sixfold to meet the demand.

“From what I have heard, everyone is trying to expand to be ready for this new market,” he said. “You want to have as many plants in the ground by December as you can. That is what everyone is saying.”

Tom Downey, director of Denver’s excise and licensing department, said a survey a few months ago found that the city’s dispensaries could triple their output based on their available warehouse space.

In the intensely private industry, rumors are flying about how dispensaries are leasing warehouses and building greenhouses to grow more pot in anticipation of next year’s rush. But the state hasn’t seen an increase in requests for grow-facility licenses.

Al White, Colorado’s tourism director, said the state isn’t pushing marijuana tourism.

“We think there are way more things to offer in Colorado,” he said. “There are probably some people who are going to stay away as a result of concerns of what they will find. There are others who will want to come here for it. We’ll win some and lose some. But I don’t think Denver will be the American Amsterdam. The concerns are way overblown. It’s not going to be as prolific as people fear.”

Denver police say they will be watching closely to make sure no public consumption occurs. And Denver hotels will inform guests about the law, said Richard Scharf, president and CEO of Visit Denver.

Scharf said the real difference will be in the media’s coverage.

“You still can’t consume it publicly,” he said. “If you can’t consume it publicly, and you won’t see it in bars and restaurants, I don’t think it will change things.”

Jeremy P. Meyer: 303-954-1367, jpmeyer@denverpost.com or twitter.com/jpmeyerdpost