My favorite scenario that could happen without totally unraveling the plot of season 6 (I sorta hashed this out with a friend a while back) would be them leaving voluntarily on a happy note in the premiere of season 7 after a farewell adventure, and then several episodes later, have a little scene at the end of an adventure like, 40 years in the future where the Doctor is randomly around dealing with some catastrophe with a new companion, and after he's finished saving the day old!Amy and old!Rory see shit going down on TV and dash over to the site of the catastrophe to see him again. With like, grey hair and retired from good jobs and friends and maybe a load of kids and grandkids.

THAT would be the kind of "timey-wimey"-ness that would actually mean something to me instead of yet another case of "oh, oh, look doesn't that blow your mind?"