Traditionally, the way it works is ThreeA or Ash will announce the sale USUALLY a week or so out. It'll be posted on their blog, various toy sites (mine included) and probably all around here. Come that sale day, you'll have 24 hours to preorder one.
Once locked down, you can expect about 5-6 months wait. Sometimes they surprise you and stuff comes a little quicker, other times it might take even longer. It sucks for your first 3A figure.. because you feel like you're waiting an eternity for it to arrive, but once you get a few under your belt, you start getting what feels a bit like monthly "gifts" delivered, which is always cool.
I imagine, 3A will handle the Marvel license a lot like they have their other licensed stuff and release a "bambaland exclusive" variant and then a standard release of each figure. The standard will most likely be available after the bambaland sale at all your fav. online retailers, though for more and with shipping generally NOT included at that point.
Hope that helps!