Quoted from toyotaboy:MJ has been saying if a reboot ever came to fruition, that a good direction might be to make the marty character female. Marty Mcfly (if we're going by his actual age of 61) could have a granddaughter that somehow gets wrapped up with the Doc again. Perhaps he makes a portable time device that can attach itself to anything with an enclosed space? i only say that because the delorean was destroyed, and traveling on a hovertrain doesnt seem like a great vehicle to get around.
They tried this concept with Ghostbusters. It didn't really play well.