This is, of course, in Finnish, but this can be roughly translated to:
"Clara saved The Doctor on Trenzalore, but entering the time stream awoke The Doctor's dark side. What if The Doctor had chosen differently on the last day of Gallifrey? A millennium as The Doctor, but what now?"
While some may consider this mere confirmation (upon "confirmation", especially due to the promotional images of The Daleks), it does also give an indication that it will be a fairly standard Moffat-esque episode with Moffat's love for messing around with time.
Interesting, however, the schedule on the official site has no mention of the synopsis, the 50th or even most of the content on that list. As usual, pinch of salt, etc.