Admittedly a lot of these articles don't amount to much more than wild guesses and wishful thinking, but I still find them fun to look at. Here's a list of what one writer considers the 3 most likely next models:
https://motoroctane.com/news/213562-3-upcoming-royal-enfield-bikesA Classic powered by the new OHC 350 seems like a pretty obvious next step to me.
A 350 Interceptor?
A cruiser with the 650? This appears to be the furthest along in development, and the sighting of an operating prototype, NOT wearing the obscuring camo decor that we've seen on a lot of early development prototypes, bodes well for introduction of this model soon, in my opinion. We talked about this back in September and it appears to be coming along.
Here's another 650 cruiser sighting article, the machine looking a bit different to me.
https://www.rushlane.com/royal-enfield-650-cruiser-pillion-backrest-12389608.html