You're probably right. It couldn't have anything to do with his loaded schedule, travelling to shoot and promote 2 shows, and finalizing the album he has coming out in October.

Summer is the only time that TV series actors can film movies or do other acting work.
Before assuming he's "too cool", maybe you could give him the benefit of the doubt
It could have been a simple scheduling conflict. Just because there is nothing listed on imdb.com that he's working on, doesn't mean he isn't working on other projects. It just means no one has added that info to imdb.com.