I always thought that the Tyros FSX keyboard is not semi-weighted keys. I actually tried to find this out for sure, but not much information in internet searches.
My local music store rep was surprised to hear about the 76 note version Tyros 5, but agreed with me that the current Tyros 4 or 3 models are not semi- weighted keys.
It's really hard to say, Marcus...I've always regarded Yamaha's FSX keybeds as semi-weighted, although Yamaha just calls it "FSX".
The FSX feels very much like the action in DX-7, DX-7II, DX-5 etc. so I tend to refer to it as such, as the latter were often called semi-weighted by Yamaha.
I really liked the DX-7, and the related synths, style action.
Whatever we call it, I find the FSX works very well for acoustic and electric piano (although I still prefer weighted 88's for solo piano work) and is a nice happy medium for covering all the sounds present on the Tyros.
I come from a piano and organ background, and I'm very pleased with the way the Tyros4 feels under my fingers.
I'm tickled to hear you're going for the new one...it's always a great joy buying a new instrument. Congratulations.