The old dev team had tried an active stargate, but it did not work out. You would start the map in a small SGC room, enter the stargate and then exit onto the map. Only one person at a time could enter the stargate. Once someone was in the stargate, if they did not exit, everyone in the SGC was stuck (New players did not understand how to exit). It was removed because of those issues and it did not add any real gameplay value. BF1942 does not have the capability to transition in-game between maps.
Will the Stargate be active in-game?
The old dev team had tried an active stargate, but it did not work out. You would start the map in a small SGC room, enter the stargate and then exit onto the map. Only one person at a time could enter the stargate. Once someone was in the stargate, if they did not exit, everyone in the SGC was stuck (New players did not understand how to exit). It was removed because of those issues and it did not add any real gameplay value. BF1942 does not have the capability to transition in-game between maps.