If you break something and you need advice, there are a bunch of long-time Campy aficionados on The Paceline, which is a cycling forum (originally it was the Serotta forum, but a lot of fans of other custom bikes or nice bikes in general hung out, so Serotta decided to spin the forum off). You may have a bike store near you who specializes in Campy, or you may not. If not, Vecchios in Colorado has repaired/maintained my Ergopower levers in the past, and I am pretty sure they’d still offer some repair services.
My thoughts on parts availability for older groups in general is just worry about it when you break something. You may be able to eBay the spare part, or a whole replacement lever or derailleur or whatever.
If you’re talking about rim brakes and nice groupsets in general, then that’s an open question. SRAM has stated they’re all in on wireless electronic + hydraulic brakes. Red and Force AXS have rim brake versions, but it’s a good bet that they won’t have a 13s group with rim brakes, and it almost looks like they can’t be bothered to update their mechanical 11s groups to 12s. Shimano’s plans seem up in the air, but 6 months ago I’d have bet that they’d still release 12s rim brake groups. I would bet money that Campagnolo will be the last of the big 3 to ditch rim brakes.
I guess that at some point down the road, it’s possible that nobody will offer a performance-level group (e.g. 105 or equivalent) with rim brakes. I don’t know when that will be. I will be sad when (if?) that happens. But I don’t plan on worrying about it because I can’t control it.
If I were building a new road bike today, I’d strongly lean towards discs, in no small part because my other bike is disc and most of the tech development dollars are going to be on disc groups. The thing is, you also aren’t guaranteed that the frame standards will remain constant years later when that group wears out. What if the mounting standard changes from flat mount? I mean, my understanding is that it is kind of finicky in that it demands pretty tight tolerances to work quietly. Maybe they come up with something better. Maybe they need a wider rear triangle because we’re on 1x15 or 1x16 groups. We don’t know either.