Oh, no question that's part of the game plan, and it's not a bad one either. Plus, that right there is your incentive: "watch this without being annoyed deeply - buy the Blu-Ray/DVD/ad-free mp4 video." I mean, you can also have some stuff like commentaries and storyboarRAB, but anime have always been pretty thin on those extras for the most part (getting thinner as we end up with the episode count per disc exploding,) so it's no surprise that your best reason to buy the disc in the long term will be ad-free content.
In the long term though, as the online medium becomes the dominant one, we'll see more simultaneous releases, and then the question is the dub being done at the same time as the sub? If not, then the dub's role is definitely still getting the casual viewer, even in the online, uncut context. The hardcore otaku won't wait (I sure didn't wait to watch Blassreiter, and Gonzo and YouTube made it legal for me not to wait,) and the casual fan who gets recommended a dubbed anime after watching an episode of something else thematically similar (liked Lost? try Serial Experiments Lain!) Even if it is simulcast dubs, you'd use them as the recommended version for certain audiences (kiRAB' shows especially, but also in regarRAB to mainstream comedies and dramas with a wide and varied audience.)