If anything, Nexus 4 and 7 demand is showing that Android is just taking off. The sooner Android moves from the OEM skin garbage, the better. It'll never truly go away, but the situation is improving. And Android is slowly taking over the tablet market. See all the reports on the Nexus 7 outselling the iPad in Japan, for example.
People who insist that Android is sluggish have not used Android in a long time. I have absolutely no idea what you're talking about. My GS3 screams. No lock ups, no lag, no app incompatibility, no forces closes, no battery problems (all problems I see on the front page of the 920 forum right this minute).
Android's not going anywhere. It's at 70% global marketshare. It'll slip, obviously, no one can maintain that kind of dominance, but as long as Android is provided free to OEMs, it's not going anywhere.
WP's biggest problem might actually be BB10. I was pretty sure WP8 would have put a stake through the heart of BB10 by now, but the tech world is pretty excited about it. That's on the folks over at Microsoft for not taking advantage of a holiday window with no BB competitor to kick it while it's down.