If you did not know, T3 Entertainment (under Hanbitsoft) talked about gearing up for Hellgate 2 a few months back. The Korean studio obtained the rights for Hellgate: London some time back from the now-defunct Flagship Studios, and managed to pushed out 2 content updates for the game.
The game engine which will be used to develop Hellgate 2 will be Unreal Engine 3, as mentioned by a senior official in the company to the Korean press. This means that it will definitely be a standalone sequel, not an update to the original which previous rumours pointed to.
The official also mentioned how sales for Hellgate: Tokyo is currently on a slump and the difficulties in working on new content for the game (Tokyo update was developed partially before T3 took over). As the project just kicked off, it will be sometime before more details will be shown.