It's too soon to be bullish on Apple's new phone: Analyst

Apple fans may be counting their chickens before they hatch, one analyst told CNBC on Thursday.

"It's just a little early to be overly bullish on an iPhone 7 that no one's seen," said Walter Piecyk of BTIG. "You can't really give them a 'buy' on some other revenue coming in over the next couple of quarters. What we're left with are numbers that are basically in decline throughout the rest of this fiscal year."

As unexpected praise pumps up Samsung's new Galaxy S7, Apple may not be able to keep up, Piecyk wrote in a research note Thursday. That, on top of new plans from mobile carriers in the U.S., prompted Piecyk to trim his estimates for iPhone sales, chopping his price target for Apple shares to $130 per share from $141.

"What we're seeing is the operators just aren't seeing their customers upgrade their phones," Piecyk told CNBC's "Fast Money: Halftime Report." "That gives us a little bit of concern over whether there's just an intrinsic change in how people are holding onto their phones longer."

Six months ago, Piecyk thought that as carriers moved away from two-year contracts toward payment plans, it would leave customers more flexible to upgrade. But after crunching the latest data, Piecyk said he was "totally wrong."

Actually, the opposite may be happening: He expects an 18 percent year-over-year decline in iPhones sold in the March quarter compared to last year.

To be sure, Piecyk's guesses fall below the average analyst price target of $134.21. Apple, renowned for its loyalists, may see a boost from the cheaper iPhone SE in emerging markets or a stellar iPhone 7 cycle later this year. But it is simply too early to tell, Piecyk said.

"You have to look at these things that could be signposts of structural changes," Piecyk said. "We've seen this kind of ebb and flow before, and the ebb, in this case, is more dramatic than it's ever been."