While they won't all open, the following teams all have a fairly decent chance of being in the market for a new coach:
-Minnesota
-Chicago
-Cincinnati
-New York (G)
-Houston
-Tennessee
-Jacksonville
-Denver
-Arizona
There's very little chance that there will only be 1-2 openings. There's plenty of time left in the season for promising starts to fall apart.
Hackett will be in the hopper with names like Brian Daboll, Joe Brady, Eric Bieniemy, Mike McDaniel, Todd Bowles, Joe Woods, Kellen Moore, Byron Leftwich, and certainly some other names that aren't coming to mind or haven't emerged.
I can't imagine that Hackett would be the #1 target, given that he isn't the primary designer or play caller of Green Bay's offense.