Screen size and operating speed could stimulate Apple's lagging iPhone replacement cycle, but with growing services revenue, that may not be quite so important anymore, BTIG analyst Walter Piecyk told CNBC on Wednesday.

"The 5 trillion [operations] per second in the new A12 chip — when someone buys this phone, it's going to operate a lot faster," Piecyk said on CNBC's "Power Lunch."

"Plus ... this is a new effective size with the screen that could induce some additional people to consider upgrading their phones," he added.

Apple unveiled its new iPhone XR, iPhone XS and iPhone XS Max on Wednesday. The iPhone XS is water resistant and offers a new processor, the aforementioned A12 chip, for faster performance, and storage space up to 512 GB. It also features an improved display for better color representation, an improved dual-camera system and a new gold color. Apple is also rolling out its largest handset to date: the iPhone XS Max, with a 6.5-inch OLED screen. It runs on the biggest battery Apple has ever put in a phone, Schiller said, and will last an hour and a half longer.

The upgrades come amid concerns Apple is suffering from slowing iPhone sales — sales were essentially flat year over year for the June quarter and Apple slightly missed sales estimates — and a flattening user base.

"Someone still with their iPhone 6 or 6S is going to be looking at someone with one of these new products, and maybe that's the type of thing that stimulates them to upgrade their product," Piecyk said.

Higher-quality products with better safety features and higher price points could stimulate users with older phones to upgrade, but could also perpetuate longer upgrade cycles. Piecyk said upgrade rates will probably bottom out at some point, maybe at three or four years.

"Those product life cycles ... they have been extending, but they've been extending for three years. You may not replace a phone that is one or two years old, but if your phone is now three and four years old, its getting a little long in the tooth and maybe you're getting some nicks on it, so at some point, these upgrade rates have to bottom," he said.

A longer replacement cycle isn't the end of the world for Apple, Piecyk said, which increasingly has services revenue to fall back on.

"In terms of the services, that's another factor ... look, the company doesn't necessarily need to grow iPhone units in order to put up double digits earnings growth," he said. "They have a long way to go in terms of [increasing] the penetration of the market of people buying subscriptions and then, also, those people that have subscriptions, getting them to buy more stuff."

Ross Gerber, CEO and co-founder of wealth and investment management firm Gerber Kawasaki, agreed.

"Their future is definitely not iPhone growth; their future is services and other products, like the [Apple Watch]," Gerber said on CNBC's "Closing Bell."

Ed Snyder, managing director and analyst at Charter Equity Research, argued that Apple should be more concerned about stagnating iPhone sales.

"The services business is dependent on people holding iPhones," Snyder said in the same "Closing Bell" interview as Gerber. "If you don't wake up to the fact people are buying your product less every year, then your user base declines. And with Apple, it's even more serious because they rely so much on services."

The iPhone XS and XS Max will be available for preorder on Friday. They will ship on Sept. 21. The iPhone XR will be available for preorder on Oct. 19 and will ship a week later.