The people I go to cons with really noticed the loss of RPGA Classic Call of Cthulhu games, along with the rest of the RPGA Classics.
A con that I help run (AnonyCon, in Stamford, CT) started producing its own pregen games to fill the void, and we've always included Call of Cthulhu in the lineup because (A) we have some authors who like writing for it and (B) there is significant player demand.
My impression is that Call of Cthulhu is much less prominent at other cons than it was, although there are still some games running. That's just impressionistic, though.
I have no idea on the sales question-- I'd be quite curious.