Thank you for sharing this interesting rumour!
However, I don't buy it. A boat ride up the Amazon river? Like, say, a cruise into the jungle, with fake animals along the shore? I somehow doubt that.
Brazil has some very interesting architecture. Portuguese / colonial style. It is very distinct, and quite pretty.
My wish list for the Brazil pavilion:
A boat ride,
where planting one guy up front means five hundred people are free to skip the line at their convenience,
where one may frantically shout and disturb the peace at will,
and that is a one way cruise to Universal.