They need to be there and in a big way, need to make a big splash. To show they mean they are for real with the NX. 
Show off what they got, make sure to include every big thing they havnt already shown off be it Mario 3D, Retro Studios game, MK9, Smash, New Ips everything. Try to get a third party publisher to get on board showing their game on Nintendos show. 2017 is a crucial year for Nintendo and they should spare no expenses  to make it memorable.

I could even see them make a return to a pressconference and show game after game, make sure to make it bombastic.

What do you think? what will Nintendo do? What should they do?

MK9 will likely be already out by the time of June 2017

Who cares about E3? All they need to do is advertise a little in Pokemon Go.

What makes you think that?

Ah the glory of showing new games in app-advertisements

Yeah, welcome to 2016, E3 is a thing of the past. We get any info leaked before anyway thanks to the internet.

Well this year they only (or mostly) showed zelda and it made a big splash.

recent Mario Kart games were always released 3 years apart from one-another so, given that MK8 sold so well releasing in May I think they might just release it in that period, in the end it'd be part of the launch window of NX and given the longevity of Mario Kart it could make up for possible drought months of Summer

this. All they gotta do is announce Pokemon Rumble on NX with full Go support on the Go App and watch the money roll in. If its a launch title I wouldn't be shocked if NX is over 10 m by the time e3 rolls along.

Nah, at E3 the hype is still fresh, they don't really need it. They better stick to their starvation strategy and only announce new stuff at TGS earliest.

Never did release during the three first months of a consoles life though, I am expecting MK9 early, but not that early.