I doubt they would shut it down, it's just too valuable.
I think it's most likely that they'd change their policies (up to and including implementing a censorship policy that extends beyond its current one that only bans illegal and pornographic content) and if that fails, they'd sell it. But outright shutting it down just wouldn't make any sense.
Would be a shame if they went as far as increasing censorship policies though. I remember around the time of Benghazi when Hillary (rather blatantly) lied about that Innocence of Muslims video being the cause of those people dying, there was huge pressure from the US government and some of the actors for Google to delete it, and they stood their ground and refused on the basis of freedom of speech. That was quite a commendable thing because of the costs they had to incur for defending what was otherwise a really poorly made video (from what I heard, I never watched it.)
I think in an ideal world, any and all content should remain accessible and shouldn't be subject to deletion, (Reddit) nor should any unpopular opinions be criminalized (Europe, who have failed to learn from the past) no matter how stupid it is. Even if the idiots are given a forum, the truth will be vindicated.
That is not to say or imply that they should have the right to sponsorship though -- far from it.