Update: Vic Gundotra, Google's SVP of Engineering, had this to say after posting on Google+ about the new Voice update:
Guys, don't worry. We have massive investment in Android. I promise you will be happy soon. Don't get upset because we show some love to Google users who use iOS. There are a lot of them. And they are good people :-)
So chill out: it looks like VOIP for Voice is coming to Android sooner or later.