Ranger REG said:
4e may change in terms of some game mechanics that gamers would like to port over to MnM rules. I'd like to say with certainty that when 4e SRD is out, that it would give Steve Kenson and Green Ronin the option to use a handful of new OGC to improve the MnM rules, or give us a book on how to use new mechanics since many of us don't play with the MnM rules "as is."
A Mastermind's Manual II might be viable. And I'm sure if/when GR decides it's time for a third edition of M&M, they'd consider any really useful changes.
However, of the changes we've seen hinted at so far, about the only ones that are interest to me in terms of M&M is perhaps whatever they do with the grappling and size rules.
The changes to saves might be viable as an option -- of course, that would change one of the big innovations of M&M (and True20): the Toughness save. So they might not want to change it; but it would be a great option for a Mastermind's Manual II (and is similar to options already in MaMa).
The skill system changes don't seem to be a real good fit for M&M, from what's been alluded to so far; they might work well with True20, but M&M's Power Level isn't the same as D&D's levels; characters aren't expected to go from PL 1 to PL 20 (or even PL 10 to 20) the same way D&D characters are expected to go from 1st level to 20th or 30th level. It would suck for a starting M&M character to be stuck at the same skill levels forever, until they get more capable of blowing stuff up.
The rest of the 4e changes so far are either specific to D&D's setting and schtick (points of light, planar arrangements, monsters), tied to D&D's classes -- neither of which are relevant to M&M -- or involve rules M&M already changed or ignored (hit points, attacks of opportunity, etc.).