I'd put good money down on them at least dipping below 60 in the Senate. I just don't see the Philibuster Proof Senate surviving 2010 at the very least.
It will not. The Dems will keep the Senate majority - but reduced.
They will also likely keep the House Majority - but even more greatly reduced.
The entire power structure within DC will be shifted - and Pelosi's term as Speaker will be done. She has offended the Democrat moderates as well as the White House with her continued partisan stupidity.
I think that Reid and Pelosi could be looking at intra-party coup attempts. Reid will probably survive 2010 politically, Pelosi won't.
I agree the Democrats are likely to keep the Senate. There are 18 Republican seats up in 2010, and 19 Democrat seats up (IIRC). If the GOP held all 18, the Democrats would still have to lose 11 of their 19 races to lose total control of the Senate. At this point (Which is still early granted), that doesn't look likely.
For the House, who knows what will happen.