I suppose that would depend on many factors. Why did the original parakeet go extinct, and what prevents the new birds from suffering the same fate? Do they eat the same foods? Does the local environment support parakeets any more?
and as for benefits or demerits – do they carry parasites and diseases that may harm the local ecosystem? Will they displace some other species which had already taken over the old parakeet niche?
lots to think about.