I think if they plan to do a parallel twin, it should look like one of the RE older twins to maintain the "throwback to the heritage" kind of retro look.
That's what Triumph and Ducati and Guzzi all did too. It hearkens back to the memory of the old "glory days", so it makes sense.
It could look something like this Royal Enfield Interceptor
If they do a V-Twin, they should definitely avoid any temptation to do a chopper-esque cruiser. That would really be "me too" in a bad way, coming in at the very end of the over-done trend.
A V-Twin standard bike or sporty bike would be nice instead. All V-Twins don't have to be choppers or Harley clones. There's a variety of ways they could go with that. They could even go futher retro, and make something styled like the old KX1140 Royal Enfield V-Twin from the 1930s., and that would have RE heritage too.
That could satisfy the cravings of some people on the "Classic Bullet Forum" who want girder forks and hardtails and that "ancient look".
Like this maroon-colored Royal Enfield KX1140 here.