Just in case you have money riding on this: The Lion King becomes the seventh longest-running musical ever on Broadway as of today when it passes another Disney musical, Beauty and the Beast. In a few weeks, the revival of Chicago will pass Oh! Calcutta to become the fifth longest-running musical…and Chicago will almost certainly stick around long enough to pass A Chorus Line and claim the fourth spot. That will occur in August if my math is correct, which it usually isn't. It would have to stick around another year and a half after that to wrest third place away from Les Miserables…and then it's unlikely to ever top the first two, Phantom of the Opera and Cats.
Phantom of the Opera is still running and all past predictions (including mine) about it winding down have proven wrong. It has had 9,539 performances and since it's still playing to 75%-80% capacity (and has long since paid back its start-up costs), it looks like it'll make 10,000 easily. We will probably not see it bested in our lifetimes.