I will be leaving for Munich on December 8th and then by train to Salzburg. I see that the current DB schedule changes on Dec 8th. When do they release the schedule for the next time frame?
I believe that new timetables are released twice a year (June and December). If I recall correctly, the current timetables appeared on the DB site a couple of weeks before June 10. For an authoritive answer to your specific question, send an e-mail to the Man in Seat 61 who hosts the best European travel site devoted to traveling by train: www.seat61.com.
DB guarantee for what they release on the bahn.de website as it's their prefered booking channel.
no worries trains to salzburg are very frequent.
About a month ahead. But the schedules hardly ever vary so I would just use the current one.