It won't really be packed, but expect it to be a little busy. The highest lines will probably be 60 minutes (expect for the Despicable Me ride, which regularly goes above), and the rest few will be in the 10-30 minute range.
Also, which park are you going to? If the last time you've been was before Potter, then you have a lot of new things to experience. IoA has Harry Potter now of course, plus upgrades to the Amazing Adventures of Spiderman, and a new Kong ride is being built which you will be able to see being built near Jurassic Park. However, the Incredible Hulk recently closed down for a lengthy refurbishment as well. US has gotten a LOT since you last went. Since 2008 it got the Simpsons Ride replacing Back to the Future, it got the Rip Ride Rockit rollercoaster, a Despicable Me simulator replacing the Jimmy Neutron Nickelodeon one, Transformers: The Ride, a Springfield area surrounding the Simpsons ride, AND Diagon Alley, of course.