Given what I know of youth today, and all the UST and sexual frustration, I'm surprised Ginny hasn't mounted Harry, or vice versa, yet. As far as Hermione, the whole 'guy shunts his girl, and another bloke gets the benefits' thing happens far too often for them not to have gone this far. Again, I'm surprised that they haven't gone a little further considering the atmosphere and circumstnaces.
By the way, did anything go into Ginny during that bed 'threeway'. Even if he didn't actually penetrate her, she could still get pregnant if some of his baby batter got into her. With the way you described things, and the mess she was after she rolled off of him, it's very possible.
Author's response
While it is quite possible, people have uprotected sex all the time without getting pregnant, so they have been lucky.
I agree, it is a testimony to Harry's self control that he hasn't given in and attacked one of them, or let things happen yet.