That would be adorable if Josie and Sam made a connection. They're quite a bit alike, now that you bring it up. I just hope they don't give Dean a love interest that isn't Cas. If they end the series at season 10, it would be VERY hard to create a viable love interest for Dean at all. Cas is the logical choice, and I really REALLY want that to happen.
I posted my original thoughts about Sam x Josie here:
http://gemwrites.tumblr.com/post/80777026403/thoughts-about-sams-love-life
I do think they’d go well together. She seems like the kind of person he could actually have a happy ending with. Of course, the fact that she's dead does complicate things a bit, but that's nothing the writers can't work around if they really want to hang onto the actress.
Right now, they’re not making any effort to set up Dean with another love interest (or even hinting at one). If they carry out the Cain/Colette thing to its logical conclusion, then the love interest should be at least part of what pulls Dean out of the MoC’s darkness— and that will presumably happen at the end of this season. We basically only have three episodes left (the backdoor pilot isn’t going to do anything to forward the boys’ story, as far as I can tell) and that doesn’t allow for time to introduce a convincing new female character, or even to kill Abaddon and suddenly have Josie turn into Dean’s Colette. Cas would seem like the only reasonable Colette parallel at this stage. That doesn’t mean they’re going for romantic Destiel, of course, but it certainly seems to point in that direction *shrugs*.