In my opinion, Schröder's statements concerning EU-enlargement are of secondary importance. Although he gained in the polls over the last two weeks, it is still highly improbable that he remains chancellor. But you are right in assuming that Germany is about to change course in its EU policy when governed by a CDU/CSU coalition: towards a slowing-down of East European integration and especially towards preventing a Turkish membership.
The rejection of the European Constitution in France also has repercussions in Germany: People became less enthusiastic about the EU in general and much more critical of EU enlargement in particular. Therefore, demanding a slowing down of the pace of enlargement could become an important part of the conservatives' campaign. But in order to do so, they will first have to agree on a campaign strategy and stop making bad news.
I would also differentiate between Bulgaria and Romania. Romanian membership can be delayed much more easily than Bulgarian membership: A qualified majority of EU membership states can postpone a Rumanian membership, but in case of Bulgaria, unanimity would be necessary.