Jon Skeet was at 95,917 rep on SO just now. What would be an appropriate power to grant him when he reaches 100,000?
How about the ability to hide exact rep, changing it to just display "Lots"?
In all seriousness, I wouldn't want any time or energy spent on this - at least not for the next year or so. In a year's time we might almost be into double digits for 100K users... I'm sure there are better things Jeff and the team can do with their time1.
1Like buying and reading C# in Depth multiple times.
I agree with TheTXI, the only level that is left is moderator, and I do not think completely moderator power should be gained simply based on achieving a certain level of reputation. Moderators have powers needed to oversee the site, and I cannot imagine giving that authority blindly to people of a certain reputation level. As you gain rep you can vote to close questions, but moderators can close with one (among other things) and that to me is a power that the SO team should be in control of, not the rep system. The rep system works well, but it is not flawless; eventually someone would reach 100k that could seriously hurt the site.