Nintendo of America registered “supermario4.com” early this month, as discovered by an IGN reader. IGN speculates that this title could be related to the as-yet nameless side-scrolling 3DS Mario game announced late last year. Of course, Nintendo is aggressive about picking up domains for names it might use, so this isn’t exactly ironclad proof of the next game’s name.
There’s also the little matter of there already being a Super Mario Bros. 4. Super Mario World was subtitled just that for its Japanese release. Are we to believe that there could be two Super Mario games with the same title? That’s just too confusing to be plausible.