Osha takes their place as guides to the north, Bran takes the place of their greensight (he's already usurped Jojen's dream about the sea coming to Winterfell), and they find some other way to ditch Rickon.

But that assumes that neither they nor Osha has an important future role where they are in the books, which I find hard to believe. The other option is that they didn't have time to introduce the Reeds here and Bran/Rickon/Hodor/Osha will meet the two of them on the road somewhere.