Over the last few years, I've noticed four trends:
-Most obvious is the rise of spend-oriented FFPs, both in the US and in Europe. This has dovetailed with the rise of credit card-generated miles (even ignoring the wacky distortions of 2020-22) versus miles actually acquired via flying. In the US, one can get all the way to top tier status (aside from the invite-only tiers) on four of the six-or-so largest carriers (DL, AA, B6, and WN). AS and UA aren't quite there (AS has a hard cap; UA has a "soft cap" in the form of per-card limits (though someone who has the old PresidentialPlus personal/business cards alongside one of the bigger new ones could get there) plus a requirement to actually fly 4 UA flights/yr).
--Own-metal flying requirements have also slid away. As of this year, as far as I can tell most of OW doesn't have the requirements, or only has them at a low level (IB) or very high level (BA, AY). I think in the US the only holdout here is UA (I am admittedly ignoring Spirit, Frontier, and Allegiant - partly because one or two of them seem to be on death watch due to shifting market trends and partly because they're not in-alliance).
-Next, over in OneWorld, a bunch of airlines are suddenly using Avios. It didn't stand out when it was just IB-owned airlines (that was no different than e.g. the LH group consolidating the program for the airlines in their group), but adding a few others changes the "feel" here. The weird bit where AC briefly sold off (and then bought back) Aeroplan also stands out here.
-Third, the rise of "equity entanglement" across airlines jumps out. DL, AF/KM, and VS are tied in a knot. Qatar and IAG are tied up. And of course, there's LH's clump of airlines and so on.
-Finally, I feel as though there's a general coordination of status requirements. Admittedly, some of this is driven by BA's new tiers looking a lot like AA's, but DL and UA aren't horridly far off on this front.

So one thing I have to wonder is whether we might eventually see a move within one of the alliances (or more) to just develop a full-blown alliance program (be it an ERM/Bretton Woods-style full interchange system, one of the programs just swamping the others (e.g. AA adopting Avios), or a new thing getting fully overlaid)? I presume it would be mostly spend-focused on both sides (earn/burn), if with some possible oddball exceptions here and there.