I agree that if Volition decides to cancel this for whatever reason they should release the source code. Keeping it locked away without releasing the promised patch would just be a big "Fuck you!" to the community. Although for now, there's nothing indicating that they have cancelled it. SRR is what's going to keep their company afloat, so it makes sense that they would want to focus on that and only that for the time being.
We'll have a valid reason to worry if we don't see any news after a couple of months of SRR being live.