Thing is Amiga aren't locked into M$ in any way, they are just a partner as was nokia until they canned the STB thing they had. I think AA/DE will run on nokia devices anyway (as well as many others).
M$ is a marketing content for their stuff only, and that content happens to be DE stuff. I'm sure if a further deal was struck with Nokia, then they would market DE software too. As the more content a platform has availalbe the more appealing it becomes.