I just found out that there'll be a demo ... but I can't update my 3DS
You could always "demo" the DS version, it's practically the same game.
This game looks to be everything I wanted in a 2D Adventure Time title, I'd love a Wind Waker style 3D game one day but that would require a larger publisher and budget...and well the likes of those tend to put out shitty licensed games. My only gripe was the actual music didn't quite fit it, a tad to "orchestral" for it. I'm more then ok with there not being an voice acting (would have ate the budget and caused the game to cost more so the publisher wouldn't have given WayForward as much time to do it) as it suits the retro gameplay.
If this actually gets a release date over here I'll buy it for DS, if not then I guess pirate and wait for the import.