I do think they're out there, but obviously very few, probably there must be instances of successful litters, but it must be far from successful breeding, watching a you tube video on Big Cats, the evidence was convincing, but there have been captive big cats of various types in this country for hundreds of years, with many escapes, with the food available, they should by now have thriving populations, but yet don't seem to have, or we would have seen far more evidence of kills, ....Wildlife, Livestock, Pets attacked, even people, yet we don't.
I think there are probably various types that may be out there, but don't interbreed very well, and from what I understand mostly any hybrid offspring would likely be infertile.
So I think what rare reports we do hear of are likely the very few that have successfully bred, and had the odd litter, and any that have survived to adulthood have scattered so making it difficult to continue breeding.
I think we'll go on hearing of the odd one here and there for years, but I doubt we'll ever see a thriving population, and if it ever came remotely close, they'd be culling them as soon as they appeared in any number.