Looks like no surprise Mario cameo will occur in Wreck-It-Ralph since the director felt he was too important to "waste" in just a cameo role but would show up in a large role if there ever was a sequel.
To add in some insult, Sonic was easily viewed as "cameo" material even though he's been the biggest rival in status to Mario.
http://www.destructoid.com/why-there...h-237197.phtml
Although people have pointed out that Jumpman is in it but under a different mane and rumors of Nintendo asked for too much money for Mario & Luigi but had no issue with giving them Bowser to use.