Great heads up.
The fact that the Colosseum, Foro, and Palatine aren't participating is a downside but I do see positives in it. Now's your chance to stop by some great places you wouldn't normally pay to see while on a visit there (i.e. - Crypta Balbi, Campidoglio). Also, I saw on their site that they're offering a variety of guided tours and lecture series in various locations, including my favorite structure the Pantheon.