On the positive side, I think they are all on pretty good terms i.e. there are no long standing bitter feuds or ego clashes (see Pink Floyd for details)
On the negative side, I really can't see where the motivation would come from. Gabriel in particular has always been very forward looking. So probably not overall (it's been 28 years!)
As musicians, all the Genesis members have moved on, and certainly none of them need the money. The urge to forge ahead with new musical ideas that obliged Gabriel to leave in the first place show no signs of abating, and since Genesis are more or less retired now, I would say there is virtually no chance of a reformation.
gabriel was also very involved an mp3 site called mycokemusic ( or something like that) that was recently sold off for a few suitcases of cash ! so he aint worried about the taxman !