I dont see a port to the moto atrix any time soon, since it has a higher resoultion then all the miui phones have, means that miui devs would have to resize all the images to the right size, in addition I dont think that theres a lot of chinese community with atrix.
if you still dont own an atrix' I would go for an galaxy s'2, I am almost sure that a miui port will be cooked for it eventually.