With only four maps I'm starting to think this will be like 1943 and only offer set kits, so here's what I think, with one for US and one for the Vietnamese: 
 
ASSAULT: M16 / AK-47. 
MEDIC: M60 / RPD. 
ENGINEER: M14 / SKS. Also, M72 LAW or M67? / RPG-2 or RPG-7?
RECON: M40 (or perhaps M1903?) / Mosin-Nagant.  
 
Along with the M1911 /  TT-33 for sidearms,but if they do have a kit system just like Bad Company 2's, what guns do you think should be included? The M79 definitely has to fit in there somewhere...

EDIT: I'm not sure if it was official but I heard something about unlocks. That would imply it there is more to it than there was to 1943.
 
EDIT x2: Forget my original point, I missed that you had the M14 already. Though, the recon could be the one using it.

I really hope it won't be like 1943 in terms of class-structure. 
 
They said there will be vietnam-unlocks and stuff, so it shouldn't be as limited as 1943.

I think they might include the R700, since it was adopted around the 60's. 

"  Mosin-Nagant.  "