I don't think so.

{xa'o na} means "already not", which would mean the event has ended too soon, but it doesn't indicate the "ending too soon" stage which would be the opposite of "starting too late".

Similarly {za'o na}, "still not" can indicate that something will start too late, but it doesn't indicate the "starting too late" stage itself.

{za'o co'a}, "still starting", might be an approximation for what you want, for lack of anything better.

{xa'o co'u} is better for "ending too soon", or "already ending".