I just noticed the new game has been released...just installed my license
As far as sandbox vs RPG....I definately would want both (even if there two different products). God mode is very addictive, and for me never gets old. An RPG version would also be fun as well. Ever since I used to play ABC Wide World of Sports Boxing on my Amiga 500 in the 80's I've been looking for a career based boxing game where I focus on one fighter and try and build my stable into something special.
To me its not a either or proposition. I want the current game and a career/rpg mode however that comes about.