Subscriber growth has been fairly linear for the last 1.5 years, tracking towards a bit under 5 million at the end of 2025. https://en.wikipedia.org/wiki/Starlink#Subscribers

Larger increases could come from opening in new areas, and increasing launched bandwidth. I don't think it will be enough, but I'm not totally sure. I'd guess the biggest markets that might come online by then are in South and Southeast Asia, but I don't have a good idea of how likely approvals are there or how big the impact will be. The v2 mini satellites seem to have more bandwidth per launch, but not radically more. V2 sats on Starship would have several times as much bandwidth per launch as Falcon 9 with v2 mini, but I don't anticipate all that many Starship launches by the end of 2025.