I wouldn't say the Dems will be in the minority for the next ten years, though. We have at least two years - but I think the numbrs (as far as re-elections) are stacked in the Dems favor in 2006.
I would say your analysis is absurd.
First of all, who is going to defect from the GOP so that they can serve in the Minority?!? No one. Not even Chafee. These guys are all about power.
As for the RATs taking over in 2006, that is nothing more than a pipe dream. I will acknowledge that as things stand right now, we appear to have more tough seats to defend than they do, but at worst, I don't see us losing more than a net of two seats. If we knock off the Nelsons, we may even wind up with a net gain of two seats.
Not even Harry Reid would share your optimistic assessment of the RATs chances of regaining the Senate.
The defections might be Jeffords-style without the caucusing. To me if we look at straight party line and assume that everyone in their party votes their party line, you are correct that it makes no sense to defect.
However, I think the dynamic of this next Senate will be different than previous. It is a VERY polarized (politically) Senate where moderates in both parties have left. In that environment, true power may come from a third group. If a centrist block is formed (and it seems the DLC is trying to accomplish this - although I am not sure how they are reaching out to Chafee and Snowe and other moderate Republicans) Chafee's influence will not be tied to his current party.
If the Dems gain two seats, and the Senate remains polarized, you can bet your farm that you will see overtures towards Snowe, Chafee.