Oliver... idk. He'll stick around NYC for a bit, watch Lucy handwalk down the hallways... and I don't know what he'll do really. See. I ruined him. I'm so boring.
Isobel... well she's off traveling with Miles and Theo and who knows what kind of trouble the three will get into. It'll be interesting to say the least and who knows where she'll end up in the end. I don't really see her doing the "get married and have kids thing" so.. Idk. Maybe she'll go to school someday and try to find something "productive" to do with her life.