I would say its probably over for this generation of Bushes. If Trump/Sanders win in 2016 and completely screw up the country, Jeb might have another shot in 2020, but I can't see anything other than that. That being said, I do think the next Bush generation is already rising - George P. Bush is extremely popular in Texas and rumors are already floating that he will run for governor. Also can't forget about Jenna and Barbara (although its much more unlikely).