I think that what keeps a lot of people involved with RISC OS, is the "what happens next" factor. Open source should provide plenty more entertainment for them (us?).
The nasty thing to say would be "too little, too late", had Acorn made this announcement in 1992 things would have been very different. Having dealt with them at that time, I can imagine their reaction to the idea.
A few predictions:
Rival versions of Paint, Draw etc.
Rival "distros", ie. rival versions of RISC OS
Entities that construct "distros" i.e. sets of RISC OS modules and applications that are consistent
Entities that control and co-ordinate development of apps and modules
More heartache for application developers ensuring compatibility with different modifications
Huge row the first time ROSL are inspired by something someone adds to RISC OS 5
Huge row as people are inspired by Select/Adjust to add to RISC OS 5
RISC OS 5 for old machines e.g. RISC PC
Paint, Draw etc. for Windows/Linux
Nothing much happens because there are too few programmers left
Martin Wuerthner adds GDraw functionality (anti aliasing etc.) to Draw module
Increase in entropy in RISC OS space