No, there was no proposal nor official engagement. The ring from the movie symbolizes the strength of their relationship and is a promise for the future - that Kirito and Asuna will always be together. It can hint the real proposal/marriage in future, but nothing more.
I am curious, all of these definite statements that it wasn't an engagement ring, are they opinion or is there something from cannon that states that it wasn't? It was what appears to be a diamond ring placed on the ring finger of the left hand. That has major significance beyond just being a ring. At least it usually does.
i don't really care one way or another, but my interpretation of the scene at the end of the movie was that they were engaged.