Apple patented the fingerdata verification techinique for mobiles in very recently infact in 2012 they filed for the patent. I do not know where they store this information but 3MB looks rather too much for just few fingerprint.
But they bought MMI for the patents more so than for the hardware. Still, now that they find themselves in the hardware business, an SoC should not be automatically ruled out. There is always a cost/benefit analysis to be done, product differentiation, etc. It really depends on Google's strategic plan with that business, and how the relationship with its Android partners factors into that plan.
That would be madness IMO. Google should focus on what they are good at (software, search technology) and partner with others in other areas. Buying Motorola Mobile was a mistake in my opinion, so to go for the SoC design business would be madness for me....
Soc wouldn't be a good investment for Google, for that amount of money (few hundred millions at least) they can achieve amazing feasts in many areas, while a soc gets only a small relative and temporary advantage.
And anyways, they managed to get unique features in their soc in the motox phone by working with others, so it's seems good enough.