Don't think it will become F2P, but close. I think it will be thrown into the X-Box Game Pass.
Edit: And yeah. If starter lvl cap is raised, I'm guessing to 30, then that would be fantastic. Two expansions worth of raids and little to no more reliance on shitty RNG upgrades for quest rewards since raid loot will just be that much better.
I thought a lvl 25 cap would also be cool, but nearly pointless. Some loot is good for that level, but most of Vanilla gear is dated besides some BoEs.
I just don't see there being a starter cap raise any time soon. Lvl 20 still provides a fuck ton of content and gearing selection. Maybe a few xpacs from now when they have to lvl squish again.