I doubt it o_o;
Every anime has sub-plots, and the main plot. The sub plots, were the jobs they were required to do. The main plot, was the one of Infinite Fortress.

The Main plot has finished, because they transferred control over to the GetBackers themselves. The fight between the GetBackers and the Gods of Infinite Fortress wouldn't really have much point seeing as the control of the fortress itself has already been transferred. But i guess there is always that chance, like Lova Hina did (Love Hina Again). But i doubt it o_o;