As a Phillies phan I share some of the concerns, but also the, "who can they get who is better?" question. (I think the answer to that is probably a Kyle Gibson type - deadline pick-up with one controlled year left - as they wait for the prospects to progress, but I'm not sure I like that answer. To do better than that would mean actually trading one of those prospects).
I think the market will probably view his struggles this year - if they continue - as more of a 2022 hangover than the beginning of decline. He hasn't even turned 30 (quite) yet. Seems like there are more older pitchers excelling than ever. Sure, it would be nice to mitigate risk with shorter length but the Phillies have demonstrated no interest in that approach thus far.
They will also have the slight advantage of maybe being able to win a bidding war simply because other teams would have to give up compensation.
They may also decide to move on, and extend Wheeler - or at least pencil in plans to do so - at the same time. But Wheeler will be 35 the first season of his next contract. And you can't really punt on 2024 when this Schwarber/JT/Castellanos core has a ticking clock, even if Hoskins is already gone and Turner/Harper have longer timelines.
I don't think it's a matter of whether or not he is a #1, more a matter of recognizing how rich all these teams are and what a #2 can get paid these days, either by a great team that already has a #1 or one who doesn't have anyone better than Nola to begin with.