Would Microsoft do it just to get time to convert Nokia customers to Microsoft customers? Seems unlikely to me.
Microsoft has earned more money from android (by lawsuits) then it earned from WP8. Maybe it is trying to earn some more by embracing and extending.
And another approach would be like, Samsung Crapwiz will look the same even if it switches to tizen or stays android. Similar to that, the latest Symbian phones already resemble androids both in UI and UX. So changing the underlying software would cause minimal attention. Nokia would only profit from this more mature and capable technology.
It would be a big f_ck to all WP devs, why would they invest in Window Platerform if all they need is a linux box to develop for MSFT phones ? But hey, MSFT works in mysterious ways.
It doesn't make sense however, as the hardware needed to run android well outstrips that needed to run windows phone well. It would make more sense to make a stripped down windows phone. So, i see no way this plan survives the acquisition.
It is a myth. The worst (and only) SoC where WP8 runs is the Snapdragon Krait. On this configuration, Android runs very well (see also Nexus 4 or Nexus 7 2013).
Added to that, WP8 phones have lower-resolution displays (Lumia 520: 800x480, Moto G: 1280x720; Lumia 1020: 1280x720, Galaxy S4: 1920x1080), which drives down the needed RAM for your framebuffer, it's backing stores, textures and assests.