Mozilla could probably survive with no additional funding, but they'd have to make some steep cuts. They have many millions in investments, enough to fund something like $20M indefinitely. That's a lot lower than their current budget, but probably reasonable if they only needed to develop Firefox.

If Google funding is pulled entirely, they'll likely find a search deal (e.g. Bing, DDG, etc), but it'll be a lot less in royalties. However, if you look at their financials, they're already putting a lot of the Google money away into investments, so they can certainly survive some cuts, provided they can something in the ballpark of what Google was offering.