Personally, I hope the book has a bit of new stuff. I loved the spells in PotA, for example... it was my favourite part of the book (my girlfriend loves the genasi).
Just speculating, but I wouldn't be surprised to see some FR-specific stuff in there. Spellplague stuff, if that's still going on. Definitely some sort of gish... swordmage would be awesome (it was one of my favourite classes from 4e, although maybe it's stepping on Eldritch Knight toes). I'd expect some class support for the Sorcerer (Favoured Soul?), Ranger (who knows what, but they know the fans don't really like it much), and I'd expect some sort of Bardic subclass. It'll probably have a bit of Realms stuff, but not as much as people will think... it'll be more along the lines of "here's the sword coast. And here's some ideas on how to convert it to your own game, or, hey, Dark Sun! Just, um, turn the ocean into silt, Elminster's a dragon king, and, uh, Waterdeep's now a slave tribe. Oh, and the harpers are now cacti. Yeah, that could work."