"We're going to spend the whole summer together," McCoy, 26, told PEOPLE at a recent record release party for label mate Tyga, in Los Angeles.
"She's going to be on Warped Tour with us, she's going to be performing. It's going to be a good time."
The 46-city, two-month Warped Tour kicks off Friday in Pomona, Calif.
Asked what he likes about I Kissed a Girl singer Perry, 23, McCoy says, "She's super hot, for one. But when I first heard the song, I was like this is going to be a smash. The next thing you know it's No. 1 on iTunes.
"I'm proud of her, she deserves it. She's been in this business for the last six, seven years, and she's finally getting a break. I'm excited for her."
So, are they music's newest power couple?
"I don't know how much power we have, but we'll see," McCoy says, laughing.
And about the couple part ...
McCoy recently bought Perry a diamond ring, but it's a "promise ring," he points out. She wears it on her left middle finger "and I have one too!" He gushed. His is a silver band that says 'Katy' on it.
"I went in (to the jewelry store) and said I wanted a ring," says the musician. "The lady behind the counter said 'here's one for $300.' I was like, 'I want a nice ring!' Then I pointed to the big one."
He admits he was "so scared to give it to her," but that her reaction eased his nerves. "She was so excited! And I'd set up flowers everywhere."
Asked if this was rehearsal for an actual proposal, McCoy shrugged ... with a grin.