I pretty much doubt that we will see another FP model this year. There is not really a room for FP4+ in my opinion, as the camera HW is good enough (unlike with FP3). But maybe they have something up their sleeve, we’ll see.
I’m definitely not trying to discourage you, it’s a great phone, but there are issues, mainly with camera, proximity sensor, call quality (or microphones in general), etc. The developers are working on it, but some tickets have been open for several months with no sign of improvement. More info here:
OneUI is “fine”. But if you want to go for clean Android, I would say it’s not a good choice for you.