I did it the last few summers. Last summer I didn't make it, so I don't know why I would go. If I got cut last summer, I don't think I'm a part of it.
Since minicamp participation is mandatory for all Team USA hopefuls, this effectively removes Lillard from consideration for the squad in the near future. He is always free to change his mind, of course.
Lillard's declaration could mean many things. It's a smart PR move if he doesn't have interest in the team and/or is too busy to participate. Ditto if he anticipates that he couldn't crack the crowded point guard field on the national team yet, or that the current coaching/selection staff isn't interested in him at this stage of his career. It's also a solid poke in the nose to the Team USA regime from one of the NBA's more charismatic young stars, a bit of payback for last year's snub. One is reminded of Mo Green in The Godfather: "I buy you out, you don't buy me out."