I don't think Harry and Chelsy will get back together. She was his first love, and most people don't marry their first love, though it's always special. They were young and suited each other at the time, but that time is long past now. Maybe Harry will marry Cressida, maybe not, but I'm sure he'll make up his own mind, as we're all entitled to. I just hope if marriage is on the cards that Cressida quickly develops a thicker skin than she's said to have because I think she'll need it.
As for a career woman marrying into the royal family and continuing with her career, I don't think it'll happen with someone as close to the throne as Harry. As has already been said, he and his wife will be needed for royal duties -William and Kate are the only 'working' royals of the younger generation, Beatrice and Eugenie want to do royal duties but have inexplicably been turned down (total madness, IMO), so Harry and his wife will have plenty to do if the royals are to be relevant to the younger people of the UK and Commonwealth. Also, whoever Harry marries will have to have permanent royal security which would be rather awkward if she had an outside job, and this would only lead to more complaints about cost, etc.
Anyway, he doesn't have to marry until he wants to, George has made Harry in royal terms less important. He's still close to the throne, of course, but if anything happened William he has an heir and will probably soon have another baby, therefore Harry doesn't need to marry and reproduce with any great haste.