An extended cut of the polarizing Prometheus is going to make its way onto the Blu-ray and DVD releases, with an estimated 20 minutes added to the total running time (which'll push it close to two-and-a-half hours).
In an interview with Collider, Ridley Scott alludes to his possible intentions for the home video release:
You're going to do an extended cut on the Blu-ray/DVD. Is it a lot longer?
SCOTT: Twenty minutes.
So there's, like, twenty minutes that will be added back in for a longer version?
By the sounds of it, it seems Ridley hasn't got a firm idea on what he wants to add, stating that he's quite happy with the theatrical cut. Perhaps he's waiting to gauge a general consensus on what people didn't like about the film and address those issues in the editors' room.
You can check out the full video interview on Collider's page.