Is Aniplex dubbing it, or is Viz dubbing it? I heard that Fate/Zero was going to be on Neon Alley, which says to me that Viz might be the company doing the dubbing. And as far as a dubbed version ever being released on physical media? Not if Aniplex thinks they might still be able to sell sub-only imports from Japan for $800.
Aniplex USA is dubbing it so they can get it on Neon Alley. Viz doesn't dub other licensor's anime. However, Viz's policy for Neon Alley is that the title must be dubbed for it to air on that channel/network/stream (whatever you want to call it).
It is very likely that Fate/Zero will get a cheaper DVD release with the dub. When I say cheap, I mean much less than the current $800 Blu-ray release, but more expensive than your average Funimation/Sentai series.
After all, Blue Exorcist and Lagrange are streaming on Neon Alley with English dubs. Has anyone heard of release dates for dubbed versions of those?
For Blue Exorcist, that's up to Aniplex USA to decide. For Lagrange, it will happen eventually. Viz's new policy is to release out the video after it's been on Neon Alley for awhile. It's a good strategy IMO. Neon Alley gives the title some much needed exposer and they can bank on that exposer with the video release.