What I'd actually be interested in seeing consists of software houses opening up the source to some of their more obsolete products. Things like early (1.0) versions of VisiCalc, 1-2-3, Mathematica, and Word spring to mind.
Id Software has already done this in opening up the sources to games like Doom and Quake.
It would be interesting, because if you recall what PCs were like during the mid 1980s, the fact that they managed to pack what functionality they did into such small machines suggests there'd be some valuable lessons in optimisation going on in there.
But I guess one reason why houses might not do this could be because an embarrasing amount of obsolete code is still being used in the current version - even if it means writing an 8086 emulator into the software so that it can run the original 8086 assembler that no-one today can be bothered rewriting. Hey, processors today are fast enough that you can get away with having your program contain an entire virtual processor on which to run antique software ... even if the result is slower than a rewrite of the old code.
Alternatively, if Vapourware Ltd. were to open up the source to FooGraph v1.0 and someone else were to use the optimisations implemented therein in a similar product with features equivalent to those of FooGraph v9.8, the result may turn out to be embarrasingly faster and smaller and, well, just more resource-friendly than FooGraph v9.8.