I agree with the fact that it doesn't matter the level of anyone in the story, if Kishimoto wants to kill someone for the good of the plot he'll do it.

But since most of you think that neither Naruto nor Sasuke are match for Kakashi, assuming that he does get there on time, what good will it bring to the story to just make him spank them both and take them back to Konoha?? None, infact most (not all) of this arc would have been useless in that sence.
Finishing the arc like that would be bad, going back to konoha and wait to get attacked again by the same guy, same plot, same story over and over again.
If Sasuke goes to Orochimaru on the other hand, it will give continuation and things would get far more interesting if he does, so the tought of getting Kakashi at least beaten by Sasuke, is not that crazy.