Hopefully they don't go out of their way to try to lock you into using their VTT. I'm not a fan of Roll20 myself but as long as they let Demiplane be themselves and keep it mostly open for third party plugins to do their thing, we should be alright in the long run.
I wouldn't be surprised if they introduce another subscription tier at some point that features Ads or worse. Then, at a later date, they will gradually raise prices across the board so the new subscription tier becomes as expensive as the current one.
I guess Roll20s subscriber numbers plateaued and they are now feeling the pressure from dnd beyond. Buying a competitor is probably the fastest way to bolster their customer count.
Roll 20 kind of sucks. They haven't made tangible improvements in years for performance, and the gm and player tools are lacking compared to other options despite making money hand over fist.
Even worse, Roll20 development is not only slow, player made solutions to issues are locked behind a paywall.
Making your customers pay you a monthly subscription to fix your product for you and then charging other customers a monthly subscription to access the fixes you didn't make is a grift so insane it's bordering genius.
Less about specifically hating Roll20, than the blatant engagement in anti-competetive practices and the monopolization of the industry in a push toward a vertically integrated monopoly.
Sort of like if Hasbro bought out the main book printer used by a bunch of TTRPGs so they have a vertical integration and can basically force all those other games to either deal with a hostile competitor to get books printed at unsustainable prices or completely upend a huge section of their development pipelines, try to find another printer, build that relationship, rework the pipeline and formatting guides so the printer actually can print the books. That's a process that could take multiple years and millions of dollars to do. Both of which options would kill even large rpg studios.