In between Robin leaving Guns N' Roses for NIN, Robin's wife Bianca gave birth to a lovely baby. It's obvious since the last NIN tour came to an end, that Robin now wants to live a more quieter life, and settle down and be with his family. Robin still pops up now and then to play low profile gigs with various artists, at a venue or at a gallery or museum. But what I can gather is that he wants to step away from the demanding touring, that touring with GN'R or NIN naturally brings.
I'm sure we all wish Robin the best, and to hope he feels free to make a special guest appearence with GN'R again to rock Better.