I guess never say never, but I'd be floored if Sark went to the NFL after this year. One, it would send shockwaves through the sport. Sark is probably the most well positioned HC in all of CFB right now. NIL, recruiting, portal, coaching staff, and Arch Manning for the next 2+ years...nobody has it better. He has a decided advantage over most of the competition.
From the NFL side, play calling and game management are probably Sark's biggest weaknesses so far at Texas. The things he's proven to be best at for Texas don't really translate to NFL head coaching. Way more parity in pro football that should take the shine off Sark for most GMs IMO.
Then from Sark's point of view, he got the job as OC for the Falcons after a short stint as an Alabama analyst. He was promptly fired 2 years later when Dan Quinn decided to clean house with coaching staff. Sark then immediately returned to Alabama as OC. The NFL can chew you up and spit you out. Why risk an amazing situation for a tenuous one?
Doubtful he would get more money in the NFL. He'd most likely take over a crappy team with a not ideal QB situation. I get that there is WAY more bullshit and travel involved in CFB, but who's to say he doesn't like it? He's clearly very good at it.