I'm speaking as a TRUE Andre Galvao fan and I know that my opinion here is not going to be the popular one... I'm just looking at this from a non-biased perspective.
Andre Galvao has a much better chance at winning the match... let's face it, he is obviously the superior athlete, and if this were a points match Galvao wins it 95 out of 100... if it were a NoGi match, those odds would be much greater.
Ryron comes from a lineage where these crazy fucks will fight for four hours straight if they need to. The Gracie style of Jiu Jitsu is typically, survive, survive, survive..... STRIKE. It is not wise to think that a fifth degree black belt is going to be a slouch against any opponent. You also have to remember that it is going to be in the gi... with handles and collars... Ryron has a shot at making the upset.
I'm still gonna put my money on Andre Galvao... but I think it will be a competitive fight...
On a final note, I feel that Ryron is being smart by speaking the way he is speaking... he is not putting any added pressure on himself, and Andre's camp is probably thinking that Ryron is scared

Could potentially be a mental game.