The dubbed movie is airing so soon? Excellent! I heard some VAs at an anime con last winter that the English cast started working on it in February, probably in anticipation of an earlier release date.
Well, we know by default Dan Green won't reprise the role here because:
(a) This Mewtwo is female, and not the old one.
(b) Dan has retired from voice acting itself because of the loss of his wife.
That leaves the question what female VA will be cast by TPCi to play this Mewtwo. It'll be interesting to see who they come up with. So long as it's not another Vic Mignogna as Keldeo type casting (IMHO, not appropriate), and more a J. Michael Tatum as Damon type casting (IMHO, very appropriate), I'm all for whoever they chose.
Awesome Pokerap: http://www.youtube.com/watch?v=DZQgrtg0uus
1. The Anime: OS > AG > BW > DP > XY (Tentative)
2. The English Dub: 4Kids + TAJ Productions (Seasons 1-5) > 4Kids Entertainment (Seasons 6-8) > DuArt Film and Video (Seasons 11-17) > TAJ Productions (Seasons 9-10)
3. The Manga: RSE > RBY > DPPt > BW > GSC
4. Pokemon: The Origin: Excellent: 95/100.
Dubbed Version: Very Good: 86.3/100.
5. The Movies: OS > AG > DP = BW
Mewtwo should be able to transform regardless of the fateful encounter flag. Mewtwo will no doubt be catchable in XY considering that nothing has been said about the movie distribution being a requirement for Mega Mewtwo. So no, the Wi-Fi event is not a pressing question unless you care about Hurricane or Unnerve.
It is the more pressing question since the film was almost certainly going to be released worldwide. Related wifi events tend to be more spuradic.
Mewtwo is concerned. It should happen before XY's release since a Generation V distribution would be awkward after that.