Actually, it would be possible for them to meet the future Marty and Jennifer, since from the future time point, Marty and Jen have already arrived back in 1985, thus completing the circuit, and just leaving the younger time travelling selves the opportunity to come forward and visit them without appearing to have disappeared.
Except, as pointed out in the article, Marty and Jennifer would have remembered their future visit and would be anticipating their future arrival (unless you explain it away by saying Jennifer was drugged out half the time and thought the whole thing was a dream).
In either event, I still maintain that going to the future effectively fast forwards time, and you don't exist in the interim. (i.e., if I freeze myself and wake up in the year 3000, everyone would think I just disappeared for 1000 years.)
I also believe that I could go back to the past and kill my past self (or my grandpa) and I would continue to exist, since I come from a place where my past self (or my grandpa) did not get killed by a time travelling me. If I were somehow able to then return to my own time and universe, it would be like I didn't exist (a la It's a Wonderful Life
). The BTTF movies don't follow this logic, because Marty starts to disappear when it becomes likely that his parents don't get married.
One other complaint is that the life that Marty assumes when he goes to the new and improved 1985 (the one with a truck and successful parents and Biff is a mechanic), he's assuming the life of some other alternate Marty, one whom he knows nothing about. His family and friends would think its odd that he doesn't have the same knowledge and experiences as the alternate Marty. He'd show up to school the next day, and probably be in a whole bunch of different classes or something.
Anyway, like I said. These are my favorite movies. They don't have to make sense for me to enjoy them, and I still watch them all on the regular.