I saw The Empire Strikes Back when it was first in theaters, and I saw it again when it was re-released in 1982, in anticipation of Return of the Jedi coming out the next year. At the end of Empire, there was a teaser for Jedi; it may have been on the same actual reel as the Empire print.
Although I do not remember that much about the teaser, and I cannot find any copies of it online, I would like to find it again. I think that it has some of the same "vertical blinds" effect that appears in this trailer for the 1982 re-release of The Empire Strikes Back (at 0:46 the first time it appears).
I am certain that it showed Lando Calrissian on the ground, struggling up the sand in the Sarlaac pit (although I do not think the Sarlaac's mouth and tentacles were visible behind him). I have watched a lot of old Return of the Jedi promos, but none of them match what I remember.