Naish's take in 2007
I came across this while while reading Dr. Darren Naish's blog on an African maneating lion of stunning proportions: the cat, now in Chicago's Field Museum, weighed an estimated 249kg. (A normal adult male averages around 180 kg). Since I've wandered onto that fascinating subject, see here.
Now, back to unknown big cats. I didn't reference Darren's 2007 column just because it cites me. I thought it a good jumping off point to mentioning that not much has happened in the big cat area of cryptozoology since then. We have some reclassifications, including debates on whether particular tigers are subspecies or full species, and the discussion of whether there are introduced American pumas living in Australia (I think there are) or surviving U.S. Eastern pumas (again, I think yes) has benefited from new reports and other evidence. But wholly new big cats might have reached a dead end with Peter Hocking's still-unresolved Peruvian cat skulls, which he reported came from new species but others have suggested came from oddball jaguars, perhaps with previously undocumented coat patterns.
Marc van Roosmalen's belief in a solid black, white-throated jaguar is interesting: I think it more likely than not that we'll get a specimen some day. But I fear the search for wholly new species of big cats may have petered out.
Hopefully, I'm wrong again.