Yes the plan is to patch BGEE and BG2EE as well. To quote Trent people would be "buckets of pissed" if they found out they couldn't play a shaman through the series.
I believe that whenever SoD comes out, a BG:EE patch containing all the engine improvements will be released to whomever hasn't already bought the expansion. This patch may or may not contain the Shaman class. A BG2:EE patch containing all that stuff should come shortly after.
After that people will be begging them to port all these new features to IWD, which may happen sometime in 2016.
Comments
Before? During? After? SoD Launches.
After that people will be begging them to port all these new features to IWD, which may happen sometime in 2016.
Obviously, this is all speculation.