Let me first note nobody has cared to answer the actual question.
My answer is: learn from 4E. That is, don't try to salvage a sinking ship - abandon it and build a new one. Look at how much better D&D is off!
In my opinion, a PF 2.5 would be the worst option. Either stick to your guns (keep supporting 2.0 accepting the game will never be nearly as huge as PF 1)) or don't (and hope you can muster a PF 3 before running out of cash).
(This comment accepts the premise at face value in order to attempt an answer to the actual question)
I agree about not trying to revise PF 2e. Better to either abandon it, or to continue supporting it but accept it will always be a niche game.
Regarding investing in a PF3e, I think their best option would still be to support 5e D&D - they have a ton of valuable IP they can pick from to convert over. IMO they screwed up hugely by not doing this 2015-16 when it was clear 5e was a huge success. Kobold Press currently occupies the ecological niche that Paizo could have claimed as the premier third-party supporter, often producing material superior to WoTC's own IMO, and with some products even competing with WoTC on sales (I find my Pocket Creature Codex is vastly superior to Volo's or Mordenkainen's for GM utility). But Paizo unlike KP has that huge backlog of Adventure Paths, quite a few of which I'd say are better than the WoTC campaign hardbacks, that could be converted into fat 5e hardbacks with a very good potential investment/reward ratio. If they don't do that, well my feeling from the sales & play stats I've seen is that they are going to be surviving more off long tail sales on their PF 1e material, and from licensing, than from anything PF 2e is likely to generate.
Regarding PF2e rules - well yeah, the 3-action economy is good. The Feat bloat and trivial bonuses are bad, like someone took the worst bits of 4e D&D and thought "How can we ramp this up to 11?"

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