Both AMD and Nvidia have been putting less work into DX11 mgpu, my guess is both are focusing on DX12 mgpu on new gen cards and with lower api overheads and better dev visibility of both cards I do actually think mgpu will make a massive step forward in the next year.
While i also hope this is the case its been stated many times now with DX 12 mgpu its more reliant on the dev and some devs are just plain lazy. Also wont help with older games