Either way, I am not worried.
ICS is plenty good for me. JB will be great once it gets official, but I'm good with ICS until that happens. I somehow think the RIL issues will get resolved.
Do you even think it will be an issue going from ICS to JB? I'm not smart enough to understand it, but they are both 4.XX ROMS, so I would think that if Samsung provides the source code, it could be used in JB.....maybe not.....idk..
RIL is closed-source, as far as I know it's never released. It's also a massively difficult undertaking, as I understand it. Because there's no source, it's line-by-line reverse engineering in smali. One change breaks everything else, and when you've fixed that, it breaks everything else again. It's a massive undertaking, and has only successfully been done with one phone and one version of Android (GB).