It's important to remember that the Mozilla Foundation does more than just Firefox -- Thunderbird, Firefox OS, Mozilla Labs, Mozilla Research, etc. all get a slice of the pie.

So while Firefox would likely survive, it'd imagine it would look much more like the post-Netscape, pre-MFL years. No more work on stuff like Rust, Servo, asm.js, things like Thunderbird would atrophy...

That said, I'm not sold on Mozilla needing Google; I'm sure they could swing a deal with Bing. What strange bedfellows that'd make.