I'm really surprised that Google is doing this. As I see it, if the service is free, YOU are the product. And in that sense, all Google users are the commodity - or their data is.
Every single call made to or from your Google number (whether through GV, the OBI, your PC, or Hangouts) goes through their servers. The call information, and very likely the content of the call (transcribed automatically, remember?) get vacuumed up by Google. Imagine having access to the contents of millions of phone calls (NSA wet dreams, I know) - but then being able to commercialize that content. As I see it, it's how Google justified keeping Voice going for free.
If you're going to go through the trouble of setting up a DID, or picking one of the upcoming ITSP OBI partners, then why on earth would you not port the number away from Google? Keeping your number with GV will continue to provide them with a record (and content) of every incoming call - and they're providing zero service for it. Sorry, but Google has become Apple.
I've already had heartburn over the NSA revelations (and Google's complicity) - so the last thing I want to do is have 100% of all of my communications go through a single company...
I'm going to wait to learn more about the partnerships. If it turns out these companies offer simu-ring, I'll port. And while I'm at it, I'll kill my Gmail (and cancer-like Google+ profile) as well. As it is, I use an outside host for my email address - and only use Google as a collection point.
Hate to say it, but Google's "do no evil" days are over. Now, what to do about my Android phone... Dangit... They have me by the short hairs.