In that respect, relax. The workbench is perfectly safe (Olsen has it) and the Shell is perfectly safe (I have it, and Olsen has a copy), so those parts are definitely not lost. Reaction is "lost in time and space", somehwere at H&P, I afraid, and it seems unlikely that we'll see sources anytime.
I'm personally missing SetPatch, FFS and Ram-Handler, components that were prepared and updated by Heinz. I'm not sure whether Olsen has the 3.9 versions of them. FFS had a couple of fixes, (ACTION_FLUSH finally working is one of them, ACTION_CLOSE returning proper result codes another, avoiding a memory leak present in 3.1), SetPatch includes a list of bug fixes that have been found (ExAll most notably, probably some stuff in Gfx), and Ram-Handler using memory pools, which is a nice addendum. Unfortunately, FFS misses TD64 support (which would be extremely easy to add, and is really just an annoyance, not a technical challenge).