Could be. That's how my experience with Panda worked out. I gained a percentage back with each update, and after about 6-8 updates, traffic was back to about 100% of pre-Panda.
Have you done something in your sites to lift the 'penalty'? In my experience, there are some factors that may help recover earlier with stronger sites, while weak sites are in a hopeless situation and there's no shortcuts unless you turn them upside down.