I'm really looking forward to this. I have a hard time believing AoA Nightcrawler will work with Dark Beast beyond returning to his own world. Beast is another one on his hit list, after all. It'll be interesting if they use the crossover to consolidate the teams in Astonishing -- give the title some new faces.
Truthfully, I'd almost rather see them turn AoA Kurt into a full-fledged villain after the event. He might make a compelling one. Then again, he might add spice to the Astonishing line-up. As long as Marvel is using the original as the poster child for "dead is dead", I'd like to see an AU version remain somewhere.
Kidcrawler is advertised to make the "ultimate sacrifice" in the previews. Hopefully they won't kill both remaining Nightcrawlers in one arc. Darkholme has more story potential, as the kid version would only end up as lame as ever and a gimmick in WatXM.
Trust Pixie Solanas to troll any thread related to Nightcrawler. You can look for it like clockwork.