Winning all four junior Grand Slams in one year would've been an amazing feat. And I guess he played doubles as well as he was going to be there anyway.
Even though he can no longer win the junior Grand Slam, I don't think Wimbledon juniors is such a bad idea either. The grass season is so short so he might as well gain experience on the surface while he can.
As for the boys' US Open event, well I don't see much reason to play it.
He's doing what I hoped he would. That is, not playing anymore junior events after Wimbledon:
Playing in what will be his final junior event before focusing on transitioning to the men’s tour, Kyrgios spoke about his desire to finish his junior career on top.
“There’s a lot of expectation being the No.1 seed again. This will be the last junior tournament I ever play in my life, so I want to go out on a pretty good memory.