Nothing would happen to Lisp. A few people would keep using it and a lot of people would keep arguing about it. Maybe Mahmud's right and there would be a new diversity of real-world applications; that would be nice.
A more pressing question is what would happen to QPX, ITA's flight search system. Google's policy of making acquired companies rewrite their software according to Google's standards would, if applied, mean rewriting QPX in C++, Java, or Python. Given how often QPX has been cited as a system that leverages the power of Common Lisp to do complex things, that would be an interesting thing to follow. I bet Google wouldn't do that, though. For an acquisition of this size (the article says $1B), the rules are probably different. (Did they rewrite Youtube?) I must say it would be neat to see Google break their no-Lisp policy.
(As a side note, it's true that if you don't care that much about continuing to evolve a complex Lisp system, it's often possible to rewrite it in a less powerful language; you just end up with a larger and less changeable codebase.)
I'm sure there would at the very least be a very long transition. And even if the core program were kept as CL code, it could still be ported over to use a lot of neat Google infrastructure.
An even more pressing question: what would happen with QRES? Reservation systems don't seem like a business that Google would want to be in, but it was supposed to ITA's golden ticket. Is selling out at this point basically an admission that this decade's rewrite of all that old mainframe code didn't work either?
(Disclaimer: just my personal opinions, not speaking for anyone else).
My guess about the problem with QRES is that after the Great Recession started the airlines that desperately want to escape their mainframe code bases now just don't have the money to do the conversion. I'm sure that's worse now with the Iceland volcano situation, which could be a money sink for many months in the future (more eruptions are possible, and this volcano has a history of triggering an eruption of a much bigger one).
Dan Weinreb said there is a lot of interest in it (NOTE, seems to be gone: http://www.youtube.com/watch?v=xquJvmHF3S8), but that everyone wanted someone else to go first, and that was Air Canada, which suspended their participation after the recession started. At that point I can see the leaders of ITA exploring all possibilities to keep the company alive.
The backend of QPX already is in C++: it loads 1/2 of a 32 bit address space with the route data. The other half runs SBCL to recommend the routes.
Depending on how tight that latter 2 GB is, I wonder if a piecewise replacement with something else that doesn't share the same GC would work well. A wholesale rewrite would be ugly ... I'm not entirely sure it would make sense for Google to do that, and they would send a bad signal if they did, as well as likely provide another proof of Greenspun's Tenth Rule of Programming (http://en.wikipedia.org/wiki/Greenspun%27s_Tenth_Rule).
On the other hand, if it's running out of headroom (address space), a 64 bit rewrite might make sense today, in which case all bets are off. The company started in 1996 and the world of CPUs and memory is very different today.
A more pressing question is what would happen to QPX, ITA's flight search system. Google's policy of making acquired companies rewrite their software according to Google's standards would, if applied, mean rewriting QPX in C++, Java, or Python. Given how often QPX has been cited as a system that leverages the power of Common Lisp to do complex things, that would be an interesting thing to follow. I bet Google wouldn't do that, though. For an acquisition of this size (the article says $1B), the rules are probably different. (Did they rewrite Youtube?) I must say it would be neat to see Google break their no-Lisp policy.
(As a side note, it's true that if you don't care that much about continuing to evolve a complex Lisp system, it's often possible to rewrite it in a less powerful language; you just end up with a larger and less changeable codebase.)