Ugh, is the reason why they cannot go back to WW2 because guns back then did not have 1 billion attachments that you have to skinner box your way into acquiring?
I can just see the convo:
Dev: We want do go back and do an awesome "black ops" game set during WW2!
Suit: Are you crazy? There were no holosights or grenade launcher attachments back then! How will we possibly get people to buy into the same game again without forcing them into another skinner box?
Dev: Well, we could, you know, change up the formula a bit and really focus on getting the best possible gameplay on these new consoles?
Suit: Change..CHANGE?!!? Do you want to keep your job son? If you do you will recreate block ops 2 but change it just enough that the plebs don't notice. In fact, advanced warfare didn't do that great so lets reuse assets and ideas from that to save money. Got it?
Dev: Yes sir .
You do realize it was Treyarch who was begging to do a futuristic COD right but IW was telling Activision not to allow them to go past the Vietnam War right?