It's a murky subject.
There's unlikely to be a 'last hurrah' of the Germans in the west, but it's also worth considering just how close to death Russia already was. The Germans sure can't conquer to the Ural, but can the Russians fight on after Kiev and Petrograd have fallen? I have my doubts, so we'd be stuck with a larger ongoing guerilla-like war with the Germans advancing (with losses) as far as their logistics take them, and the various peoples of Russia rising up (esp. in the Caucasus on the back of Turkish advances, even if these advances are only a thin veneer on the actual nationalist movements).
At some point, either the Germans crack in the west or the Russians come to the table anyway, hoping they can just cancel the treaty once Germany loses (and thinking that'll hurt less than Germans taking Moscow, or Kazan, or Volgograd, too).