PF2 is coming at a good time for my group. I've been running a long term homebrew campaign with a 30+ page houserules doc that is about to end. It's a good time to try something new. We'll probably try Starfinder first, but PF2 is on the horizon for us after that.
What will I miss the most? Probably the system mastery and strong opinions that I've picked up over the years. I built a lot of that mastery by practically memorizing rulebooks in high school. I don't really have the patience to do that anymore, so I'll probably never know another system as well as I know PF1.