It honestly has a lot to do with how many orders the various ASIC companies have and how quickly they can a) catch up on backlog, and b) fill new orders quickly.

My prediction goes well above 1000TH/s, but this takes into account:
--BFL catching up on all backlog (thousands of orders) and shipping in a timely manner (not this day-at-a-time nonsense).
--Avalon catching up on Batch 2 and 3, as well as disclosing any future plans.
--KnCMiner developing and shipping according to their schedule.
--BitFury (and other hardware developers) receive their chips (either Avalon or BFL), boards, and parts so they can complete their devices.
--ASICMiner continues to increase their deployed hardware (including sales) and discloses future plans as well.
--Other unknown or still in development projects / companies.

There's a lot of factors at play at this point..vastly more than any of us could have imagined just 12 months ago.