Ok now, I'm a bit confused...

[Lwerewolf]

The guy I asked (blizzard artist):
http://phillgonzo.deviantart.com/
Quotes from the conversation, check the comments (it's quite recent):

Didn't imagine I'd find a Blizzard artist here
Anyways, a question:
What battlecruiser is the Hyperion in SC2? I mean, considering that it looks just like every other BC in the game (except for in-game), then either it got upgraded to hercules/minotaur or all battlecruisers are behemoths (unlikely but still)... Just don't tell me you scrapped the SC1 art
And what's the reason for the visual consistency between the in-game and cinematic model

Answer!:

The size classification of the Hyperion is Behemoth-class. Behemoth class is intended to be the common Battlecruiser rollout, we unfortunately didn't have time to create a unique model for the Hyperion.

The initial intention with the cinematic model was to showcase the Hyperion as a unique flagship. Eventually time constraints didn't allow us to make uniquely different versions and ending cinematics called for multiple Battlecruiers on screen at once. We had to work with what was available.

So... Does that mean that the cinematics battlecruiser is, in fact, replacement art for the behemoth-class?

[Thalraxal]

Certainly sounds that way.

He's got an interesting collection on his DA gallery though. It's kinda neat reading about what went into designing all of the different units. I think I'll keep my eye on his gallery. Kinda hoping we get to see more of the ones that didn't make into the game, but I'm not going to keep my hopes up on that. Thanks for the link, Lwerewolf!

[Lwerewolf]

Was certainly hoping that the old art was cannon... Ah well, it's just my taste, maybe.
*curses like mad*

[Chriso]

Wait, what, Behemoths are the StarCraft II battlecruiser? I thought they were Hercules-class?

[Lwerewolf]

"Behemoth class is intended to be the common Battlecruiser rollout, we unfortunately didn't have time to create a unique model for the Hyperion."
It might be that the hercules-class are still too new or something for them to dominate the number of behemoths present - after all, the dominion was left in a pretty bad shape after the brood war and the first record of a minotaur-class vessel is from 2502 - 2 years before the SC2 events, 2 years after the brood war. Still that doesn't answer how so many behemoths survived. Otherwise, odds stack up in favour of the model being a behemoth... sad.