Democrats are not taking anything for granted and are focused on keeping seats in 2010. The New York Times reports:

The president’s top strategists have recruited candidates — and nudged others to step aside — in races in Colorado, Illinois, Massachusetts, New Jersey, New York and Pennsylvania. They said they intended to continue this practice heading into the 2010 midterm elections, as well as with an eye to the redistricting fights that will go on within states early in the next decade.
The intense involvement reflects the tactics and style of the White House chief of staff, Rahm Emanuel, who helped Democrats win the House three years ago as chairman of the Congressional campaign committee.
While some party officials applaud the White House for its efforts — there is widespread concern among Democrats that the party could suffer if Mr. Paterson runs — the actions are drawing alarm from some Democrats who believe they cross a line and run contrary to Mr. Obama’s often-stated pledge to rise above partisan battles.

Joe Biden says bluntly, via ABCNews.com:

if Democrats were to lose 35 House seats they currently hold in traditionally Republican districts, it would mean doomsday for President Obama’s agenda.
Biden said Republicans are pinning their political strategy on flipping these seats.
“If they take them back, this the end of the road for what Barack and I are trying to do,” the vice president said at a fundraiser for Rep. Gabrielle Giffords (D-AZ) today in Greenville, Delaware.
Republicans need to pick up 40 seats next November to take back control of the House.
There are 49 seats currently held by Democrats in districts that Sen. John McCain (R-Ariz) won in last year’s presidential election.
Biden said these House seats are Republicans “one shot” at breaking the Obama administration’s agenda. But if Democrats can hold on to those seats, “the dam is going to break,” he said, and a new era of bipartisanship will begin.
“All the hidden Republicans that don’t have the courage to vote the way they want to vote because of pressure from the party … it will break the dam and you will see bipartisanship,” Biden said.

Remarkably, of course, Dems do have a hold on D.C. at the moment and it’s still as hard as it has been for them to even get their health-care agenda into legislative form. Significant losses next November will, I think, permanently remove some of the glimmer from the Obama rose. And really create an opening for an active and constructive opposition. The resulting Congress might be the GOP’s last shot before the next presidential election to prove they don’t blow all opportunities given to them.