I don't know how much influence Bremen will have, though. But it's in the interest of the SPD not too stick too tight with the grand coalition, they don't want to perpetuate it forever, after all.
So, let's speculate and say there will be a red-green coalition. The next elections in the German states are January next year, in Hessen and Niedersachsen, and after that Hamburg, in the second quarter of 2008, and Bayern, in the third quarter of 2008. That's four more states before the next Federal elections.
I don't see Bayern going to the SPD, and Niedersachsen is going to be tough. The SPD+Greens need to gain 10% in both Hessen and Niedersachsen, and 8% in Hamburg (in Bayern, over 25%). Will we see an end to the grand coalition if the SPD manages to get a coalition with the greens or the linke in Hessen/Niedersachsen?
P.S. In Berlin, the linke were divided, and lost more than they had to. In Bremen, they were united and gained a lot. Of course, in Berlin they were in the government, but I think the story is clear here.
While working-class Frankfurt and the Protestant Northeast may be SPD strongholds, the belt of Frankfurt (where I lived) was mixed, the sides of the Taunus are full of well-off conservatives, and the East (region of Fulda) is dominated by an arch-conservative CDU. (Do you remember the Hohmann affair? "Tätervolk"? He was from there. [Incidentally, one eighth of my ancestry also came from there.]) *Lunatic*, n. One whose delusions are out of fashion.