Biggest deals are probably the shift to creating armies with "warbands", plus new deployment scenarios; plus some new rules from the new Hobbit book, specifically for monsters (very welcome changes) and new heroic actions (very nifty options).
Warbands require a hero + up-to-twelve warriors, and your armies are composed of multiple warbands. Gone are the days of Legolas + 40 wood elves
but even if you're a fan of WE, it's a good thing.
Otherwise the game is the same, you won't have to relearn everything. If you want to be up to date, get the Hobbit rulebook, plus the latest six sourcebooks: Kingdoms of Men, Free Peoples, Fallen Realms, Mordor, Moria/Angmar, and Desolation of Smaug.
As for OOP stuff, yeah, it's continuing, seems like they're phasing out metals, and not always replacing them with Finecast versions. So get 'em while you can, I guess.