I was surprised and amused in equal measure when Gabriel said he wanted to do Supper's Ready on his 07 tour (he apparently faced open rebellion by his band and quickly dropped the idea).
I am a huge PG fan but quite frankly, I stopped listening to him when he talks about possible Genesis reunions or solo albums for that matter, loooooong ago.
He, of course is at a point in his career, when he is more than entitled to do as he pleases. He had his say, received critical praises and enjoyed commercial success. The whole package. He was highly contradictory and frankly a bit haughty when he tried to explain why he wasn't interested in a Reunion. as he was more interested in looking forward than back. It would have made sense, if he hadn't then released an album with 10-years old songs in some cases already released on other albums i.e. Sky Blue and I Grieve and then a couple of orchestral, cover albums. Way to look forward Pete! Just do you thing, you don't owe any explanation, particularly when it's a ridiculous one.
As for Steve, playing Genesis, perhaps it's the cynic in me but I have the feeling the considerations behind it are purely financial ones.