I think there is a chance he's playing around to dump her when he finds the proper woman to marry.
Stop dreaming guys, you are looking at your next lazy Princess. I will tell you why
1) Harry is at the point where he is ready for marriage. Any female that he is serious enough to step out with at this stage will become his wife
2) She is ready to "Take it on". That imo is a very crucial factor. Chelsy left because she could not take it on. Harry practically confirmed this much during his interview. Harry knows this is the deciding factor
3) No woman will be ready to step out with Harry now because she knows she will be crucified by Cressida's crew in the media as well as the Yorks being hostile because she threw a monkey wrench in their plan. Harry's wife has to interact with this lot should she marry him. Who wants to walk into such a hostile environment
4) Where is he going to find another vapid chick who is ready to wait on his beck and call and has no other driving desire except to marry well.
5) Harry probably knows how determined Cressida's crew are and that they might fight dirty if he drops her and steps out with someone new. He knows how exhausting it is trying to ensure that he steers clear of situations where his ex and current gf will meet. It is not a very comfortable position to be in. Trying to show affection to your current gf without seeming to disrespect your ex. Now Harry knows that this is fairly easy with Chelsy because (a) Her family are in AFrica not London, b) she is not on a media campaign to hook him (c) Chelsy is not an attention seeker plus she is too busy to go swanning around.
WIth Cress, he knows this will not be the case. She has no job, will be swanning around so he is very likely to constantly run into her and her crew EVERYWHERE . Talk of ACKWARD. So where will her take his new GF
6) The media will have a field day writing about why they split and this may end up hurting Cressida badly. In spite of everything, I think he is not a thoughtless person. Plus the press will be in media heaven comparing Cressida and his new GF.
I am very sure Harry has thought of all these things. It is just not worth the hassles. And lets not discount the fact that he is probably relieved that Cressida is ready to take it on after Chelsy said no. He is not your average Joe Soap, he comes with a lot of baggage so it is not just a matter of who he loves, it is more a matter of who can take it on and fit in well. He practically said so himself
So I say to all you who said they will not marry, to STOP DREAMING and go buy a hat for the wedding before all the good ones are gone