By 2024, approximately 94% of all bitcoin's will be mined, and block reward will stand at 6.25btc. Unless a massive adoption event occurs that causes TX volume to jump exponentially, it is possible that by 2024, or past 2024, miners will no longer be sufficiently incentivized to "mine" as good actors.
Well there's always proof-of-stake.
In all seriousness though if they're able to push through the increased block size it will set a precedent and other possible future changes like POS might not be unthinkable.