Google has announced that the 2015 I/O event will take place on 28th and 29th May with registrations opening next month.
According to the Google I/O website, registrations for this year's event will be open from March 17th to March 19th. However, registration does not guarantee entry to the event. Google will be employing the same lottery system as last year to pick out people at random out of those registered. Each person can only register once.
As of now there is no information about Google's plans for the event but the generalized schedule has been made available here. Those who do not get a chance to attend the event can catch the whole event online.
The main bits of news we can expect from Google this year includes the recently launched Android 5.1 Lollipop, the future of Android One devices and maybe some information about any upcoming Nexus devices.