Google is getting ready to release android 5.0 Jelly Bean already, while most phones are still running 2.2 Froyo and 2.3 Gingerbread.
Faster updates - (HTC sense and samsung touch wiz will be easier to incorporate into the OS so updates will come quicker.
Better / Advanced Keyboard
Lite version of the OS for lower class phones like my LG thrive and O-one
When will it be realesed? Some say that it will be second quarter this year, or fourth quarter.
So if you have $400 to waste, go but the Samsung galaxy nexus (data plan, minutes, texting chatges WILL apply).