Hey there,
Besides Raspberry Pi and x86/x64 platforms, we’re starting to roll out Volumio 4 for our devices as well, starting May 4th. You can find all the details in this thread.
A reflash is only required on Raspberry Pi and x86/x64, for our products there’s no need to: the update will show up directly in the app once the image for your device goes public (or about 10 days earlier if you want to join the beta, the process is covered in the same thread).