I had a terrible thought. What if Deadpool is the last member of the team? He's been in a dark place lately, and it'd coincide with the Wade & Piotr team-up in the Deadpool film which coincidentally comes out in May.
We got it over in Ultimate X-Men when that was a thing too (alternate universe but kinda counts). It's not particularly innovative, and it put's a lot of the eggs in one basket so to speak, but if it boosted sales then Marvel would probably do it.
It would explain why they're all hush hush regarding the final member of Astonishing. It doesn't change the fact that I'm not overly invested in the team. If anything, Logan on the team is a detriment (for me anyway).
It's possible Astonishing #13 is set after Hunt for Wolverine, freeing him up to join the team.