Everyone commenting here seems to take this to mean he's leaving Google, when that's not what the article says.
I’m willing to bet a lot of money that the “chairman” role is a contractual obligation and he be will be gone the day it expires.
omg, you are right, he is leaving google!
Clearly his influence is going to be less though.
And most likely this is a calculated step to avoid freaking people out, even though he is effectively leaving.