Battlefield: Vietnam will be a whole new game. It will still use the Refractor 2 engine (or they would be saying how cool their Refractor 3 engine is by now).
You should just expect redone physics (thus not being able to die by falling 5 feet), higher quality models, better sounds (considering 1942's are crap), and optimized net code.
It really isn't changing much, just enough to go with newer hardware.
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