Oh, definitely. All the extant bipedal animals are pretty decent at what they do in various ways (the ostrich uses its wings as rudders to steer at high speeds, which is neat). It just seems that large cats are their greatest enemy, and probably a much bigger obstacle to their success than other carnivorans like dogs and bears. Big cats have successfully hunted both apes and flightless birds for millions of years, and would probably give kangaroos a lot of trouble as ambush predators if they ever found their way to Australia.