Saw this "rumour" online....
http://www.diszine.com/content/will-wor ... w-pavilion (http://www.diszine.com/content/will-world-showcase-in-epcot-get-a-new-pavilion%22%20onclick=%22window.open(this.href);return%20false;)
I remember reading they have room for about 4 more countries or something and its been a while since the last new one in the late 80's.
EPCOT deserves a new country and since South America isn't represented at all, I think Brazil is a good choice.