Yeh i dont think it would be present day...
Although im now thinking Acensions takeover by zombies happend the same time as FIVE, i don't have much proof although one of the red phones plays JFK's "Beans for the chowder" which; just like in Shi No Numa, you could hear the marines from Verruckt fighting when listening to one of the radios in the swamp. People believed the events of the swamp and verruckt where happening at the same time.
So with the red phone playing JFK's quote and a quote i heard when playing ACENSION with Richtofen last night "Hmm this future is an interesting place" something along those lines if not exactly that, this makes me believe that our characters have possibly travelled from:
Der reise (WAW)>> forward in time too >> Kino >> then however they escape from kino and end up on the Lunar pad which drops them in ACENSION.
I believe the zombie maps from WAW went in storyline order they then time travelled from Der Riese to KINO which makes me think all B.ops zombie maps are al happening in the same time frame.
Next up? Who knows.. Moon?, America?