No... it wouldn't happen. Maybe you saw a Mandalorian Helmet that looked like Revan's. It just wouldn't happen, it would break the lines of canon and it would make things weird.
He couldn't have been a spirit, because the longest we've seen one last is about 300 years.
Plus I think GL doesn't evne know of Revan's existence, and if he did he'd probably retconn Revan. Because quite frankly he wouldn't like Revan, I don't. Well I use to like him till after that horrendous book.
They toyed around with bringing both Revan and Darth Bane out to play during the Mortis Arc, its in the behind the scenes. http://starwars.wikia.com/wiki/Ghost...ind_the_scenes