I/O is in May.
They haven't launched a Nexus device at I/O since the OG N7. Doesn't mean they won't, they just haven't used I/O for Nexus launches for a few years now.
And just for fun, MWC is going on right now. The S7, G5, and a few other phones have been announced already and are running the Snapdragon 820 or the new 650 for the mid-range.