A Lieberman aide was quoted yesterday in Politico as saying "His position is he wants to remain in the (democratic) caucus but losing the chairmanship is unacceptable." The CW now is that Reid is buying time to see what happens in the other Senate races still to be decided, before he ousts Lieberman.
Another angle on this is that Lieberman may be threatening to leave the Democrats, but he won't find a lot to cheer about if he goes further over to the dark side. He will likely not get any chairmanship, will be in the minority party, and will have even less clout than if he stays with the Democrats and gives up his chair without a whimper. So, for good reason, many Dems are saying "Let him go!"
Bottom line is that the Dems may not need his vote if we pick up another Senate seat. With Maine's moderate Republican senators, its likely that they would support President Obama on moderate issues, and would break the Republican's threats for filibuster. They both saw which way the wind is blowing, and doubt they will repeatedly vote against their constituents wishes on major issues like the Iraq war and the economy. Lieberman may have just threatened his way into irrelevance.