A customer holds a bottle of flavored vape juice while exhaling vapor from an electronic cigarette at the NXNW Vapor store in Sacramento, California.

Some have called Food and Drug Administration Commissioner Scott Gottlieb's resignation a boon for the e-cigarette industry, which Gottlieb has repeatedly attacked for fueling a surge in teen vaping.

The impact of his abrupt resignation, however, may not be that simple.

Gottlieb in September declared teen e-cigarette use an "epidemic" and threatened to pull products from shelves if things didn't change. He called in executives from Altria, Juul, British American Tobacco, Japan Tobacco International and Imperial Brands. In November, Gottlieb said the FDA would pursue an effective ban on convenience stores selling fruity flavors of nicotine.

Gottlieb's threats pushed Juul, the company he blames for the teen vaping "epidemic," to halt sales of most of its flavors and shutter its social media accounts. In February, he accused Juul of going back on its word after the San Francisco-based start-up took a $12.8 billion investment from Marlboro maker Altria, and he called the CEOs of both companies to his office.

Despite all of his passion and bluster, Gottlieb wasn't as tough on the industry as he could have been — or as his successor might be. Although tobacco stocks jumped on the news of his resignation Tuesday, it's too early to say how Gottlieb's resignation will affect e-cigarette companies, industry executives told CNBC. They also fear his successor might abandon regulatory efforts altogether, exacerbating youth use and causing Congress to step in.

Gottlieb has come under fire for delaying a 2016 rule that would have allowed the FDA to start removing e-cigarettes from the market this year. It was a move the industry applauded but health groups often often criticized. He avoided directly restricting e-cigarette companies from selling the flavored products he has blamed on a surge in teen use, something lawmakers have pushed.

"He could have [reversed the application extension], he could have tried to pull flavors from the market. So certainly his words were the issue and not always his actions," said Gregory Conley, president of the American Vaping Association, a group that lobbies for "sensible" regulation of vaping products.

Even though Gottlieb talked tough on teen vaping, he championed e-cigarettes as a tool to help adults ween themselves from combustible cigarettes. Smoking kills nearly half a million Americans every year, and few people successfully quit.

E-cigarettes are considered a less harmful alternative than cigarettes, though their long-term health risks remain unknown. Cheryl Healton, dean of New York University's College of Global Public Health, praised Gottlieb for navigating the complex and fierce debate.

"The information on how helpful e-cigarettes are in people trying to quit and how harmful or not they are for young people is a moving target, and it's always hard to set policy in an environment in which you're dealing with one or more moving targets," she said.

Gottlieb won't see most of his tobacco policies through. At an event hosted by The Hill on Thursday, he said the FDA will implement the e-cigarette flavor sales restrictions before he leaves in about a month. He also said he expects his successor to continue the work he started.

It will take far longer for the other Gottlieb-led regulations to take effect, if they're even pursued.

Within months of taking over in 2017, Gottlieb unveiled a sweeping plan to lower the amount of nicotine in combustible cigarettes to minimally or nonaddictive levels while trying to get more adult smokers to switch to e-cigarettes. He has also advanced a plan to ban menthol cigarettes and flavored cigars.

Gottlieb's replacement may stick closer to the Trump administration's script of rolling back regulations, not adding them. Though lawmakers are likely to press the appointee about teen vaping during confirmation hearings. Just last week on the Hill, lawmakers grilled Gottlieb on the issue.

Although some industry executives are celebrating Gottlieb's departure, "no one should be cheering too loudly" since Gottlieb's successor has not been named, Vapers United spokeswoman Liz Mair said in a statement.