Your are partially right. But the underlying thought is that such a scenario is possible. Germany's electorate structurally supports - from 1949 apparently until now, although the end might be in sight - the government of a moderately conservative party with a strong socialdemocratic streak.
I agree, and probably Freivolk, too, that you cannot prevent the SPD from winning a federal election now and then, especially when they allow someone who from their right-wing to campaign. But one cannot help but notice that every SPD-led coalition on the national level only clung to power very narrowly after their first years in office. The aforementioned structures within the electorate recover rather fast and led to the very narrow wins in 1976 and 2002. In both cases, a return to power of the CDU is anything but impossible.
1972 and 1980 are rather exceptional to the point that extraordinary circumstances allowed the SPD to thoroughly mobilize their voting base. In 1972, this was due to the CDU's reluctancy to accept the necessary - and also, 3 years was apparently not enough for a conservative backlash, in 1980 due to the mistake of putting Strauß into the field.
I would argue about the "unrecognizability" aspect. The German political mainstream is not that far apart from each other, esp. CDU and SPD to achieve that. And the problems remain the same, whether we change some bits of who is in charge. The balancing aspect of the Bundesrat is also a key element in that. But expect for Schröder in 2005, who IMHO simply lost his nerve, the majorities in the Bundestag never caused a federal government to break down. As in the US and France a sort of "cohabitation" is a normal element in German politics. Add to that the fact that most field of politics are either federal or on the state level. This also hinders "state politics to become massively changed".
Also note that while the duration of SPD-led governments gets shorter, the general swings remain the same. Actually, we get one more swing with the chancellorship of Hans Apel.
One could also argue that a FRG where actually Roland Koch is Bundeskanzler isalready an absolutely unrecognizable thing.
One more point: I could well imagine a 2010-election not leading to a 3rd CDU-victory in a row, especially if Stoiber might have sent the Bundeswehr into an Iraq equivalent or the economic crisis hits Germany differently.
@Freivolk: it would be interesting to see what coalitions you might envision. Red-Green in 1981 seems out of the question. Rau still tried to rule that out in '83 OTL. Also, the history of the FDP might be a very different one, as they are the weakest ones when it comes to fighting butterflies, IMHO.