Google bids on Yahoo!

No, they haven't, and I doubt they will. Google's competition is not really Yahoo or Microsoft. It would be Ask, except Ask is old and it's too hard for them to get new users.

If Microsoft buys Yahoo, they'll probably screw up on search, and that will leave lots of room for a newcomer

Google will save their money, and when the next search king comes out of the woodwork, they will buy it. And then either integrate it, use parts of it, or bury it.

(It won't be Wikia, but it will be something like it...)