The CS:GO devs have hinted via Twitter that they will be replacing de_nuke with de_train in the Active Duty map-pool come next operation.
With discussions of the need to reinvigorate the map-pool after the static, same seven maps have continued throughout multiple majors, the official cs:go_dev Twitter account has tweeted that de_train will be replacing de_nuke in the Active Duty map-pool in the next operation.
The decision may be influenced by the perceived one-sided nature of de_nuke, with the CT bias being on clear display at ESL One Katowice 2015, e.g. map three of Virtus.pro versus Keyd Stars.
Although this announcement does not mean the map-pool of the competitive circuit will change in any shape or form for the time being, it does suggest future changes to the competitive map-pool that may mirror this move, as well as the possibility of map tweaks for de_train (and less likely, de_nuke).
At Katowice we let the pros in on a little secret: next operation we're updating the Active Duty map pool, replacing Nuke with Train.— cs:go (@csgo_dev) March 20, 2015
The new version of Valve's de_train was debuted in December after the map disappeared off of the Active Duty and competitive map-pool early in 2014.