Currently the Bahn website cannot allow booking beyond 14 Dec 2013 which probably is due to their annual schedule alignment/changes.
Yes, you right. Second weekend of December is standard timetable change date almost all over Europe
When will itl be reverted to the normal 90-day out booking?
Unlike other railways Deutsche Bahn is usually rather disciplined in terms of entering new schedule into the system and allowing booking, so based on previous years experience DB starts ticket sale for new schedule around mid October (max. end of October). But at the same time take into consideration that with some international trains it might be not the case, since here DB depends also on other railway companies, so obviously they can't start ticket sale unless everything agreed with foreign rail companies.
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