It's never too late, but people have to understand that the games been around for awhile, so they may run into some unobtainable things - although, Blizz is doing a decent job of putting a lot of stuff back in through things like the black market AH.. anyway
As for the death of wow, I foresee it hitting the 20 year mark before they start pulling major people off the game. It will be officially 13 years old this Nov, and again 7 more years isn't as long as some people think. They may just keep the game on perm life support at that point for another decade-who knows. I highly doubt we will see any game as successful for probably a 20-50 years.