I know this topic has been covered dozens of times, but some comments really sparkle my doubts, because I think I remember quite well their relation, and I don't think there is a "Goodbye at a bus stop" before she parts to Paris. I only remember she being on the last episode of season 4 (Paper chase/ Mallory's Graduation) and then Alex talking about her on the episode "Starting Over" - 502.

I'm relatively sure there is no "real" goodbye with Tracy Pollan on stage..
Am I wrong?

I agree - it was just stated that she had already left for Paris. Maybe they're referring to when she and Alex are dancing and the song "What Do You Think (I Would Do At This Moment)" plays. It's supposed to explain Alex's feelings about her leaving.

unless they got married in real life

MJF and Tracy Pollan didn't get married until 1988 and she was already off Family Ties by then. I kind of wish that they would have had a "real goodbye" for her.

I kind of wish that they would have had a "real goodbye" for her.Me, too, especially since them becoming a couple was so major. That is still one, well two of my favorite episodes. I saw them when they originally aired. And them dancing to "At This Moment" ... talk about chemistry, WOW! I never quite felt it like that when he was with Lauren. Just my two cents.

I think it would have been interesting to have an episode where Ellen tells Alex she's leaving. Instead we find out in the next season she left because of a dance scholarship in France.

In real life, Tracy Pollan didn't want to continue to be on the show. She had a boyfriend, not MJF at the time, and she wanted to be with her boyfriend.