I'm very concerned about this, because if it goes through there will be a direct competitor to Physics.SE. Every time I look, the proposal has more support. Yet right now 4 of their top 5 example questions fit well within the scope of physics.
We already suffer from low traffic here, and a site solely dedicated to astronomy has proven to not be viable (probably because there are hundreds of good resources for amateur astronomy already out there, offering interactive sky charts, photo galleries, and day-to-day distillations of recent publications). Yet here they are trying to carve off a piece of physics to make another attempt, and it's not clear why. Note that I am in astrophysics, and I enjoy "amateur" activities more than most people in my field, but I can't condone driving a further wedge between Earth-based physics and everything that happens off this planet.
So regarding (1), donating material to the fledgling site, as charitable as it may seem, would be shooting ourselves in the foot. And as dmckee rightly points out, this probably won't be an issue anyway.
For (2), I suppose we should recover anything that fits within our scope that we don't already have, and I'd gladly help out. That said, it seems a little much for the powers that be to expect us to clean up for a second time after the same experiment fails again.
Finally, I'd like to know if there's any way to formally bring these concerns to the SE powers, via a petition or something. (I never fully understood the enigmatic forces behind this whole network, but that says more about my ignorance than anything else.) Of course, if no one agrees with my concerns, I'm willing to go with the flow of an informed populace.
[End rant fueled by years of exposure to passive-aggressiveness between physicists and astronomers.]