It is too easy for partisan Democrats to gloat about the apparent collapse of the Republican Party. Some have even speculated that the Republicans will go the way of the Whigs, replaced by a new major party (say, the Libertarians). Others suggest they will simply be out of power for a long time.
One way or another, the Obama Administration is doing all it can to further the GOP's self-destruction, trying to prop up Rush Limbaugh, or selecting a Latino for the Supreme Court in what has predictably provoked a backlash from Republicans who will alienate a potentially valuable bloc. (You really think Obama didn't anticipate this when he selected her?)
Nevertheless, this situation might not be such a great blessing for liberals in the long run. Competent, sane conservatives are leaving the GOP in frustration. If they join the Democrats in droves, it risks changing the party's character. Progressives already complain that the Democratic Party has moved to the right. You think the situation will improve if disillusioned ex-Republicans flood the party? Maybe we should be encouraging the sane conservatives to keep trying to fix their old party instead of diluting ours. It may be difficult, but it will be better for everyone in the end.