First, let see the history of FreeSpace 2 :
Volition Inc, the company responsible for developing the game FreeSpace 2 was bought over by THQ in 2000. With Interplay Entertainment holding the licenses for the FreeSpace series, Volition could not continue to develop the series. Without any viable use for the source code, Volition released the source code for FreeSpace 2's game engine on 25 April, 2002...
For a similar situation, Stardock need to hold the license for SOASE, Ironclad need to be buy over by somebody other... So, Ironclad will not more be able to use the SOASE source code and maybe they will release it...
I don't think that it will happen... the iron engine is relatively new, have some huge potential when the code is expand to 64 bits and multicore... in fact, it is very possible that after a SOASE 2 and a SOASE 3, the engine have become so much good that Ironclad can maybe license it for some other games...