It stands to reason that if the stocker CBR1000rr piston fits (probably, as someone mentioned, having too much clearance due to the head design) then the high-compression Wiseco 1000rr piston should fit as well. The wrist pins are the same, as is the diameter. The only things that are unknown are the valve position and clearance, skirt shape/size, and balance issues associated with the stock 250r balancer.
The biggest thing I can think of, both in a positive and negative light, is the possible difference in head surface/valve clearance and how it relates to compression ratio. I'm ready for someone, anyone, to give it a try.
I plan on doing it as soon as I relegate my 250r to a track/fun bike rather than a daily-commuter/fun bike, likely after I get a larger sport or supersport in a few years. In that time I hope significant advancement has been made with the motor, as I feel it has great potential, if based on nothing but geometry alone.