First, this is really hillarious, listening you argue both sides of the argument in EACH of four posts. But you make good points, both of, er... you.
Anyway, my one point to add to this is that M3 more than likely will not go into huge amounts of detail on things that do not directly involve its story, so there will still be lots of information in GURPS which is not replaced by new information in M3. So you see the problem; if we discount GURPS entirely, there are suddenly huge holes in our understanding of the world outside late Wind, early and late Wolf, and early Sword ages.
So I think that unless MJ release something equivilant to GURPS, explaining the entire Mythworld in their updated, corrected detail, then we should consider the non-contradictory parts of GURPS as well. Though it occurs to me now, TFL went into some detail about Connacht because the main bad guy, Balor, was Connacht reincarnated. So since Moagim Reborn was Moagim of the Wind Age, and Tireces of the Age of Reason, there may very well be reason to elaborate on those ages in Myth III, as they have effect on the immediate story the same way Connacht effected TFL.
