I don't think we'll ever get Melee-style Target Tests back ever again. The roster is very big now and so making 50+ stages for the roster would require a lot of work.
That really depends...we don't know how long each aspect of DLC the team has been working on...it is possible that they could've started work on a Break the Targets or Adventure Mode since the base game finished development, knowing that DLC will be possible and they'll have an extra year or two to work on it...
Characters do take a while to make but that doesn't mean they are only focusing on said characters and nothing else...of course that's just a 'what if' Angry Target Bird Blast is likely all we'll get in that regard...
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On another note, Just imagine how much different the game would've been if Sakurai would've focused solely on Smash for Wii U instead of making a 3DS version...
Ice Climbers
Wolf, Lucas, Roy, and Mewtwo would've likely made the initial roster (as a result possibly better DLC characters in their place after launch)
Dedede's side B with Waddle dees instead of just Gordo's
Olimar would have more pikmin
A proper Adventure Mode or even a SSE 2
Break The Targets
MORE NEW CHARACTERS...and stages...
It could've been possible they would've been able to sell more Wii U consoles as well since I would imagine a lot of Smash fans that owned the 3DS wouldn't even bother getting the other system for a game they already have...
this version of Smash seems to have had a lot more compromise than any other version simply because of time constraints...