Anything is possible. Most flu viruses are fairly stable most of the time when it comes to the species they stick with in nature, but then species do not live together often in nature. However we humans have created artificial environments where various species live close together leading to a much higher chance that a virus will jump from one species to another. Not too long ago Horse Flu jumped to Greyhounds at the (a) race track, now we have dog flu. Thus far there have only been a few rare-ish occasions when humans have reported picking up the flu from a cat (or dog). We do know that this H1N1 (swine) flu has jumped into several species and has the ability to jump species easily. We have seen it jump from pigs to humans back into pigs, we have now seen it jump into cats. It also has trace markers in its genetic make-up that point that it has mixed with Avian flu and common human flu(s). Thus it is possible that it can jump the species barrier both ways in Cats, dogs and other mammal species that can contract flu. Horses, Dogs, Humans, Birds, Whales, Pigs have their own species defined influenza variants, some of which we have seen in the past (and present) jumping into other species.