After an interview with Thing_Ting today about the future of Mario Builder he revealed that the game was near it's V12 stage and announced that Mario Builder will be
making it's way onto Smartphones starting April 10th.

Here is what he said about Mario Builder V12:

I am near the completion of Mario Builder V12 and many Mario Builder fans will be excited to here the news of some of the newest …

Mario Builder V11 -

-Many kinds of enemies can be placed ontop of a pipe opening. This will cause them to continually spawn from that pipe.
-Added an invisible text block
-Added the pink piranha plant by Alju5 through the engine challenge
-Added the ice bro by lukasmah through the engine challenge
-Added Ice bro to the overworld
-Boom Boom and Koopalings must take multiple shots …