Version 5.1 Beta 2 already work on RX480, but you won't be able to see the temperature from claymore, which I think the watchdog will be useless.
For Linux user is the same and worse, since there is no alternative software to see the temperature ( adl3 - atitweak no longer works )

The good part is windows and linux now has the same hash speed in mining, since the driver will be at the same level between both OS.
Overclock only works using windows and with the stock amd software. I'm not sure is vbe7.0.7 and atiflash can oc this one since they are incapable to oc since R9 380.