That engine package is fairly new, and some clubs here in Cali are still testing it, and some have already raced them with very good results.
I hear nothing but good things about it, that the bottom end is a lot beefier with a 125 cc crank and bearings, that it is screaming fast and reliable, etc.
The only issue I’ve heard so far is that the onboard starter is having some issues, but they’re working on it, as they don’t want it to become an issue like we’ve had in the past with Rotax and Leopards.
Your question about piston life is a question you should ask a shop, seller, supporter or a team that supplies those engines, as far as I know they are still trying to make it grow, and I know of a guy that is willing to let racers borrow engines to test them and see how they like them.
And the answer to your other question about the future replacement of KT100 is correct, not only the KT100 but will also replace the KPV for sure.