Nah, the Sith had a super-long plan, and force foresight can't warn them.
He may have found out something coming after the fact, but then just used it as an excuse on Thrawn, without truly knowing the scale of the threat. If it doesn't show up, good. If it does, fine, he can use that.
Sidious is a manipulator or liar who has no problem giving people justifications that'll work on *them* but have zero to do with his real motive.
Originally posted by Emperordmb
IIRC (and my memory's pretty hazy) some dude who captured Wedge said the Empire would've shat all over the Vong.
Conversely, Han Solo pointing out the opposite, that they would've made stupid wasteful moves.
And the Emperor's fall demonstrated how vulnerable the Empire's structure is- a lot of high ranking people in it are only in it for themselves. The Vong infiltrators will actively use that to recruit and splinter things, just as they attempted to undermine the Republic.
That said, the unified galaxy will win, period, and the New Republic was not in the best of shape beforehand, so the Empire may well do better, but it does have it's own problems.
Worst-case scenario, they manage to take out Palpatine and the Empire splinters mid-fight.