As wyrwulf said, Eovia didn't explain in details what will be their upgrade policy . All we know is that there will be upgrades for RDS, Infinity-D and Carrara 1 users to Carrara 2 . If i'd recommend Carrara ? Yes, if you can find it at a low price ! It's still buggy but a patch release is planned . Even if Eovia allows you to upgrade from RDS 4 to Carrara 1 ( low chance, IMO ...), the upgrade price will probably be quite high, so ... litst