It's possible, but one very promising lead has been run to ground.
This is a case I worked on myself: I took Peter Hocking, the discoverer of one and possibly two possible new cats in Peru, to Denver to meet with a mammologist several years ago, but all we had were photographs of a skull, and Dr. Cheri Jones, the expert at the Denver museum, thought that inconclusive. Hocking thought his “speckled tiger” might actually a be a jaguar, but a previously unknown color morph, while the “striped tiger” (reportedly rufous in color with white vertical stripes) was more likely to be a new species. If this proved true, Hocking would have had the first new big cat species described in nearly a century and a half.
Now another friend of mine, Darren Naish, has taken up the case. He and his collaborators, including Hocking, have been disappointed. It appears the Peruvian finds must have been unusual jaguars - VERY unusual, in terms of reported coat color, but otherwise that trail has petered out. When reading this paper, also note the excellent recap of recent mammal discoveries and discovery trends. We have by no means catalogued all the mammals of Earth.Here's the paper!