How to Upgrade Ubuntu core snappy from 15.04 to 16.04

I have Ubuntu core running on a Raspberry Pi 2 stuck on

Linux Porzellangardine 4.2.0-1024-raspi2 #31-Ubuntu SMP Tue Feb 9 11:44:25 UTC 2016 armv7l armv7l armv7l GNU/Linux
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 15.04
Release:        15.04
Codename:       vivid

But this month 16.04 will come out. Will there be a way to upgrade a older version of Ubuntu core, or must I re-flash it to get the newer release?

EDIT: I found out, that 'ubuntu core' and 'ubuntu core snappy' aren't the same. I didn't find any 16.04 version of ubuntu snappy yet.