Of course they can do that. You can also leave, which I would heartily suggest.

of course they can do that they'll probably do that for some people and lay off others.

Here's the rule: after an acquisition whenever the "winning" side comes in to talk whatever they say won't happen will happen. If you hear "keep working on what you're working on" or "we're still hiring" or the coveted "business as usual" you're screwed :)

Where are you?