I think that new upgrades may be coming out, check out this image from RS's site.
It shows the blue, orange and yellow motors with square caps. I thought that the blue motors were only offered in the Inital D and Fast and Furious kits had round caps. Correct me if I am wrong, but this looks like a new motor/gear upgrade kit, but it doesn't show up on the RS site yet.
Edit: I just realised it is the Purple motor not the blue that was offered in those kits and I always get them confused as they are difficult to tell apart in pictures. Sorry for the confusion everyone.