The next Iterations of Mario will actually be a 3D revamping of Mario bros 3 and Super Mario World. The overworld nature (where you can select which level to play) will come across much like LoZ's Ocarina of Time, or in the more restrictive case of Mario Bros 3, will play out much like Twilight Princess. Each individual world however will play out much like the paintings in Mario 64
To add to the difficulty of the game, enemies that hit mario while he is in one of his suits will be able to knock his power away from him and steal it, creating tanuki goombas that can turn to stone and Hammer bros Koopas with harder shells, but this will be a feature that can be exploited as well, such as placing the stone goomba on a switch to keep it activated, and using the Hammer Koopa's harder shell to surf into blocks that wouldn't be able to be broken with a normal koopa shell.
This game will also bring back mini mario, as mario will only have 3 iterations of life(just as in Mario Bros 3 and Super Mario World) Mini mario will be able to jump just as high as mario, adn even fit into places regular mario can't, but will lack teh fighting ability that regular mario has.
In order to counter the harsh difficulty of only having 3 segments of life, instead of mushrooms only coming from boxes, they will be able to be found scattered all over various levels. Super mushrooms (allowing mario to go into GIANT mario mode) will be the mushrooms that come from blocks.
Along with this, Mario will be able to find be able to find a satchel for carrying numerous items around in the overworld(like in mario Bros 3), as well as a plumber's toolbelt that can be used to carry a select number of items with him through the individual levels(like in Super Mario World, except allowing for upgrades to carry more items)
Essentially, the storyline will start out with mario bros 3, where Bowser has kidnapped princess, and has his kids transforming the various kings. After beating bowser the first time you will have the cutscene where they all go out to yoshi's island to celebrate, upon which Bowser captures her yet again and the game then continues, following the Super Mario World storyline.
Yeah, I put way too much thought into this type of stuff.