Not sure about Force and all-out, but I think Krayt would win a sabers-only fight.
In a sabers-only situation, Wyyrlok has proven himself to be competent enough to not get stomped by Krayt. It was definately a one-sided duel, however.
Celeste/Muur was roughly equal to Vong Krayt. The gap between Reborn and Vong Krayt is quite large, however (Reborn Krayt has shown he can speedblitz those who would give Vong Krayt a good time, in Cade Skywalker), so I doubt that would be the case here. I'd say Celeste/Muur would perform about as well as Wyyrlok did.
This will be a tough fight for Krayt, but he has already proven himself capable of handling multiple individuals trained to fight in groups at once, in the Imperial Knights, and Wyyrlok didn't appear to be able to mount any sort of counter-offensive against Krayt, so I doubt Celeste/Muur could, either. Krayt wins this in a tough fight.