I'm going to be the contrarian here. Sight unseen, their design goals seem to require a certain degree of backwards compatibility, even if by accident. If I'm going to be able to sit down with a (focused) group, create characters, and run a simple adventure during my lunch hour, the most basic characters cannot be much more complex than BD&D ones, combat can't be 3E or 4E-level complexity by default and adjudication has to be, at its simplest level, something a DM can determine or wing very easily.
Now, will there be things that aren't in previous editions, like condition tracks or classes and abilities that don't map directly over to older editions? Of course. But those will likely be the exceptions and I don't think it'd be that hard to either wholesale incorporate them into other editions or replace them with older edition equivalents.
I'm looking forward to, at the very least, pillaging a lot of the sourcebooks and adventures (assuming there are good ones again) for C&C.