End game is where a lot of fun comes in.
Raiding: You and up to 39 other players (40 total) go into dungeons and take on extremely challenging bosses for epic drops that are far beyond anything that you can buy. You and up to 39 other players can also go on city raids, or PvP raids. For instances you can go raid Stormwind with your pals :).
PvP to the Max!: A lot of players enjoy the PvP, there is a small minority that will talk about the good ol' days on this or that game where the PvP was amazing but for the most part the end game PvP is fun!
Level Again: Your probably like, "Why would I want to level another character?" It's simple, you have lots of gold, so you can 'twink' him through out his levels by giving him/her great gear.
Farm Gold: Maybe your the type that just likes to have a lotta gold? Well you pick up great gear for long grinds, and you go farming for gold. After a farming session you return to the bank and sell stuff via proffessions and from the various items that you have found. I have been able to make up to 20-100g a day at about level 48 or so on my shaman, so at 60 possiblities can becoem better!
In conclusion I'm not sure why I'm wasting time typing this, but I feel that you should have an oppurtunity and know what's out there waiting for you :) :). You can do a lot, because hey your 60! You no longer have the restrictions I'm to low for this or that, I can go do it because I'm 60!
-JonM.