I think that's probably the right grouping, and I suspect a D&D that really focused hard on levels 1-10 and making sure they were fun as hell would be significantly better than ones trying to cram 1-20 (or more!) in.
Also, if they release the others a year or two later, that gives them time to correct mistakes and see how things work out.
I think anything less than 1-10 is making a serious mistake because what you're creating is a "stopping point", and every time you do that, people get off, whether the game is good or not, people get off. I'm sure that in the longer-term, BECMI was hurt by that more than it was helped by the relatively lower prices and simpler rules that you can have with the smaller level brackets.