The RC390 looks a lot like dropping the 390 engine in the RC125.
I wonder if the chassis can take the 690 without major modifications.
I would like the toy should they make it at a manageable price.
A WERA Racer in the US has done it and told me it's not huge project - frame mounts needed to be changed along with some other adjustments but overall in his opinion KTM could make that bike a reality with next to no R&D expense and using only products already in use on various bikes.
My ambition outweighed my talent.