Like both previous posts, I think that sales dictated the fate of the 77x series. I think the 806D2 also fell to the same fate. The 806 is a great knife but I just don't think that the sales were enough to keep it going. It's too bad to, it is a great knife and so is the 77x.
I have a 773BC1 and I love it, very smooth action and a sharp little sucker to boot.