My prediction for Google I/O this year:
Android 4.5 or 5.0 (leaning towards 5.0) will be revealed and then projected to release around mid-late July. They're going to name it with an L (Lollipop or Licorice) and get away from the Kitkat name. I'm going to assume this is because of licensing using the Kitkat brand name for a limited time and the reason why 4.4.3 came out so soon was to fix the bugs before moving on to the next major version.
While I was watching previous Google I/O keynotes I stumbled across what Android Police reported the other day as Quantum Paper (
https://www.youtube.com/watch?feature=player_detailpage&v=9pmPa_KxsAM#t=3922 ) and (
http://www.androidpolice.com/2014/0...upcoming-effort-to-make-consistent-ui-simple/ ) and judging by the amount of work that they had last year to a year after, it'll still be in its early stages but will probably take a major role in the next Android version with the app and UI design. And all of the tools will be integrated in the new SDK for developers to easily use.
Android will be using a new colour scheme and will be more flat with the new major version. It'll use darker colours instead of the brighter colours in the design guidelines but will still use it (
http://developer.android.com/design/style/color.html ). All Google apps will move to their own colour instead of using the grey action bar like on Gmail or Calendar. Think of the new Google+ update.
Circle iconography will also be introduced like the Google I/O 2014 app. This will probably happen sincce Google seems to be liking circles nowadays (Hangouts, avatars in Hangouts, Google+ logo, etc)
ART will finally be in a usable state and will debut with Android 5.0. Hangouts will add Google Voice support and maybe introduce a better looking UI but look the same-ish. Google Cloud Messenger (GCM) will be big in in 5.0 and that's what Project Hera will be. Think of Google Docs but system wide and it uses GCM to do it.
Google Play Services will also be beefed up and I could see the next version being the last one for a while. It'll practically control most of Android and can push some updates without the use of a full firmware update.
I know i'm forgetting more but pretty sure some of this will happen judging by rumours, updates, and previous things Google has said.