No, unfortunatley not. Surreal had plans for a possible 3rd game but it was only a 'maybe' which would have been considered after they had released a few other non related games first. Even then, the decision to go ahead or not would be up to its publisher, Sony Computer Entertainment.
Surreal, however has been bought by Midway games to work on games exclusivley for them so that means they definitley won't be making another Drakan. The Drakan series is owned by Sony as they bought Psygnosis inheriting all of their trademarks of which Drakan was one of them.
So, for a 3rd game to happen, Sony would have to get another developer to make the 3rd game which is unlikley going by the poor sales of The Ancient's Gates. The other way is for Midway to buy the rights back from Sony and have Surreal make it which is equally unlikley. Shame really, if TAG had done very well and sold as well as lets say, Tomb Raider, <ahem> they might have made a sequel or two.
It all boils down to money and sales figures unfortunatley.
Weclome to the forums BTW!