The Atlanta Thrashers' ongoing projected move to Winnipeg will have a ripple effect throughout the NHL if it does indeed happen before the 2011/12 season. The NHL re-alignment would have to begin immediately, and it would start in the Southeast Division, where the Washington Capitals reside. Someone is going to have to replace the Thrashers, unless the league decides Winnipeg can be passed off as a Southeast city.
So who could possibly move into the Southeast? A couple possibilities below the jump.
Stephen Whyno of the Washington Times ran through a number of options a couple weeks ago, and my guess is they haven't changed much since then. The option that makes the most sense geographically would be to have the Nashville Predators switch conferences and move into the Southeast. Someone (maybe Minnesota or Colorado?) would then have to take Nashville's place in the Central, with the new Winnipeg franchise moving to the Northwest.
But there are a couple other options too. Two teams -- Detroit and Columbus -- would desperately like to get out of the Western Conference because they are in the Eastern Standard Time zone, whereas Nashville is not. For Columbus, it's about giving themselves more of a chance to compete, since they always get buried by the West's strength. SB Nation's Blue Jackets blog The Cannon analyzes the situation in depth here. If the Blue Jackets move, they'd probably move to the Southeast instead of either of the other divisions, kick-starting the same process we'd have with Nashville.
If it's Detroit that moves? Then, it gets more complicated. As an Original Six franchise, the Red Wings will probably have more sway with the Board of Governors, who must approve every realignment decision. The only problem is that there's no way Detroit can move to the Southeast. With the Blue Jackets, it's at least sort of feasible to say they're a Southeast team, since they really aren't an Atlantic or Northeast team. With Detroit, it's pretty clear that they're a Northeast team. This would then force one of the five Northeast teams (either Boston or Buffalo most likely) to move to the Atlantic, which would cause Philadelphia or Pittsburgh to move down to the Southeast. That seems pretty unfeasible, since you can't really break up the Penguins-Flyers rivalry.
No matter what happens, we know the Capitals will get another division opponent if the Thrashers are able to complete their move. It's just not clear whether it will be Nashville, Columbus or someone else.