It's not bankruptcy in the sense that they're selling everything to pay their debtors though. That's Chapter 7.
Under Chapter 11 THQ gets a certain amount of time under the supervision of a bankruptcy court, to reorganize into a more viable business, in order to pay their debtors off in the long term.
Of course, there's no guarantee that they can turn themselves into a viable business, so I think it's safe to say that if THQ slips up even a little in 2013, it's going to be final.
Based on what I can find out, Chapter 11 usually means the company becomes delisted from the stock exchange, and the shares are made worthless, which I guess leaves the buyer in this case with a chance to start fresh, while the previous shareholders lose everything.
I would expect the letter to make you aware of that, if that's the case. Doesn't it say you're losing your share?