Yeah, the usage of V instead of 5, as well as the ESRB rating mentioning drug use (the first in the series to mention drug use), had alot of people expecting Vietnam. On top of that, the EA/DICE marketing team had teased a brand new setting for the franchise on the official Battlefield website, so alot of people were hoping for the Korean War, the only major war in the 20th century to have not had a video game based on it so far.
WW2 is not a new setting for the Battlefield series, they already did it with Battlefield 1942 and 1943. Why did they not just name it Battlefield 1944, a name that was in-line with the other WW2 Battlefield's, and announce the name last week, instead of naming it V and teasing a new setting for the franchise, getting people hopes up for other settings for no reason?
What would be a new setting?.
We had Nam in Bad Company 2, in the form of DLC, going back to it with more nam based maps and a nam based campaign wouldn't exactly count as being "never done before".
We've had other games touch upon Russia, Germany, United Kingdom, Japan, and the USA. What we haven't seen touched upon are the wars in China, Korea, Italy, Poland etc.
I would honestly want something new, or at the very least, a popular war, rather than one that wasn't popular, involved a fuck ton of Napalm and involved the US losing said war. We know how WWII went for sure, but we also very much knew how Nam went, and especially how that ended.