Blizzard remodeled the graphic of the banelings. And now they don't roll to attack the enemies. They just run like other Zerg ground units (except the hydra which moves like a snake).
Banelings without the speed upgrade run, Banelings with the speed upgrade roll. People will instantly know if Banelings are upgraded or not, without having to eye-measure their speed.
GMG beat me to it. They indeed only roll with the upgrade, which means that in the match we saw, the Zerg player did not upgrade his Banelings. Not really something I'd do, but what do I know. Haven't even played the game yet.
The timing of both BR 3 and when Blizzard changed the upgrade are unknown. (We know when BR 3 was released, but not when it was played.) My understanding is Gasmaskguy is correct, and I believe something similar was done with zerglings. (Not hydralisks though.)
Zerglings get wings with the speed upgrade. As for when BR 3 was played: at least two weeks before we got to see it. You know, since Blizzard said that it takes a while to localize the game in all the languages they want it in. It was said by multiple of their community managers, so I guess it's pretty accurate. I'd be surprised if they actually got in done in just a few weeks. Lastly, the walking form of the Baneling looks silly. It's just to fat. However, it's of course strange that such explosive creatures can just roll over any terrain type without spontaneously exploding. And then I'm not even talking about "steering" yet.
I'm sure there was a video of that matter wherein the upgrade made it very noticeable and was even mentioned by the commentator.
