Possibly, Russia is engaged in a major military build up at this point and Germany's own estimate was this would make victory impossible by 1916. Get that far and the combination of a balance of terror in the East and the end of the anglo German navy race might put off the war for good or at least a generation.
That said Germany has a ticking clock, Russia has been decapped at the start of a potential major crisis and Austria is out for Serbian blood. Lossing Nicky could make war more likely not less because the Germans may calculate that kicking them when they're down is the best option here.
But they need some excuse (it was still an era of trying to look decent
Possibly
To quote Mr E Blackadder "He brutally cut his head off whilst shaving," unhappy accident, nothing to see here.
Well, I still think that biting it off sounds more ...er... natural.