I suspect it's just the next in a line of cost saving redesigns for the PS3, or just restocks.
However, I don't think something will be released in July. And I think this rumor is completely false.
Remember that a very big game is coming out for the PS3 in less than a week. This means they'd want to have as many systems on the shelves so that people can buy them with the game.
Also, if you look at the release dates for July, there is nothing there that's popular enough to create a while new bundle of.
The only reason I can think of why they would withhold models is that those boxes really are the the latest redesign of the PS3 hardware, and with the PS3 likely selling a lot of consoles in June with MGS4, they want to clear out all the old stock of costly PS3s before introducing the more efficient ones to market.