I don't see how this would affect google much, if at all.
Look, google is primarily a services company, whereas apple is primarily a products company. I don't think enough people truly understand this. Having deep facebook integration will negatively affect one minor google service (google+) and leave the major ones untouched.
If Apple wants to kill Google, they can't do it via products. No matter how good the iPhone is, google will win. Why? because google's services runs ON the iPhone. Every time someone does a google search on their iPhone, or check their gmail account, or watch a youtube video, or checks their location in maps, Google is making money.
To kill Google, Apple has to either:
1) Disable or prevent Google's services from running on the iPhone (unlikely) or
2) Develop their own alternative services to Google, and make them the defacto standard ones to use on the iPhone (much more likely).
Of those 2 choices, 1 is not going to happen, as it will pretty much neuter the iPhone. 2 is possible, but I find it unlikely that Apple will create more widely used search, video, maps, and e-mail services (and those are just the big ones) than google's; nor do I think it will make financial sense for them to do so.
So what is Android to Google? Android serves two purposes.
First and foremost, it is a means to an end to get as many people using Google's services on mobile as possible. Why do you think Google gives Android away for free, and continue to brag about activation numbers? Because every person using Android is also using (at least one of) google's services, and that is where they make their real money.
Secondly Android serves as a contingency plan in case Apple ever decides to pursue either choices 1 or 2. In either case, even if Google loses the entire iOS market, they wont' be completely locked out of the mobile world altogether.
In the end, it doesn't matter to Google if Apple kills Android. Hell, a while back, it was revealed that Google makes more off iOS than they do off Android (don't know if that's still true). If every single Android user went out and replaced their phones with an iPhone tomorrow, Google will be just as happy in the short term; though the same can't be said about Samsung, Motorola, and HTC.