I have no idea if there is an OFFICIAL change in AMD's stance for or against crossfire. I know that directx 11 supports crossfire and sli, if the game and your drivers do. In direct x 12 it supports multi gpu and new standard, which theoretically allows even different cards to work together, you can google this where some are having good luck even with one nvidia and one amd card.
Now IMHO and a popular shared opinion of, I would guess many users and game developers, is that crossfire and sli introduce way more problems than it is worth. think that statistically way more people are using dual or more cards than in the past. One issue is that the card makers are no longer allowing you to do it with mid level cards and lower anymore. So really it is only an option for the very high end users. So when you statistically look at it like this, you are programming something special for maybe 10% of the gamers out there. Then you realize that less than 10% of the driver user are gamers to begin with. This is a pretty small amount of people to code for in the grand scheme of things. My hope is that the lack of support right now is more because so many developer are focusing on their new Direct X 12 and Vulkan engines and we will see better support for multi gpu setups in the near future than we ever had thus far. Again this is just my take on things, I don't claim to have any really accuracy or insider knowledge here.
Good Luck & Happy Gaming!
