That seems like a lot of options to explore at once, and could be quite expensive from an R&D and product development standpoint, while at the same time failing

That seems like a lot of options to explore at once, and could be quite expensive from an R&D and product development standpoint, while at the same time failing to capitalize on large returns to scale. Rather than a 4-pronged strategy I'd rather see 2 pronged strategy. Keep Android, dump WP7 (it's a laggard and Ballmer's MS seems incapable of generating any big wins) and select one of either MeeGo or Symbian.