Eventually Russia will attack ISIS. But right now, they are trying to not fight 2 fronts at the same time. As the turkmen showed with killing the pilot, they are the current target of Russia now. And if it's true that ISIS is funneling oil through them, the strategy by Russia is sound. Close off the Turkey border, which will mean ISIS will lose a good portion of their funding. Which will mean they will be an easier target to destroy, since their biggest strength is hiring people who have no other means for a job.