I think there are at least a few of big downsides to Nokia releasing some Android phones. First, and most obviously, their software team would then be supporting three operating systems, and their efforts will be further diluted. Secondly, Nokia explains its simultaneous support of both Symbian and Meego by arguing that Qt-everywhere means that all their smartphones will present a single API, so their phone lineup really isn't fragmented, from the perspective of app developers. But Android meshes poorly with the Qt-everywhere philosophy. Thirdly, there is wide speculation here and everywhere else on the net where Nokia is discussed, that Nokia is going to abandon Symbian and Meego and adopt Android or WP7. If Nokia does actually start shipping Android phones, many app developers will see that as the start of an inevitable All Android strategy for Nokia. Would you bother writing commercial apps for Symbian and Meego when Android is growing rapidly, has already passed Symbian in market share, and Nokia has started building Android phones too?

I think Nokia must either abandon Symbian and Meego, or stay away from Android.