He’s joining for this upcoming tour, but it could easily be the group’s last major tour. I don’t see this as being permanent. Neil is too restless. Perhaps it will make him want to dust off his own band. Who knows. But I don’t see this as the end of anything, but rather something full of new possibilities.
That said, I’ve never been particularly interested in Fleetwood Mac, but it’s a very high-profile gig that will expose Neil to a lot of potential new fans. It also opens him up to the scorn of a lot of die hards. Hopefully people give him a fair shake; the initial reaction from FM fans has largely seemed like “Nothing against these two replacements, they’re very talented but it’s not FM without Buckingham.” Hopefully it goes well and Neil and Mike Campbell change some minds.