Reason why they decided hole E3 2016. only to Zelda BotW is because they didn't want to talk about Switch games yet that they were saving for January presentation, so E3 2016. was exaption and really can't be compared with any other E3.
But it's very obvious that Nintendo has staffs to show through the year:
-January: Kirby, Mario Aces, Dark Souls, DKTF, The World Ends with You: Final Remix, Hyrule Warriors: Definitive Edition, Ys VIII: Lacrimosa of Dana, Celeste, Mario + Rabbids Kingdom Battle DLC, SNK HEROINES Tag Team Frenzy, Labo...
-March: Smash Bros, Splatoon 2 Expansion, Okami HD, Sushi Striker, Captain Toad: Treasure Tracker, Travis Strikes Again: No More Heroes, Undertale, Crash Bandicoot N. Sane Trilogy, Little Nightmares, South Park...
-May: Pokemon Let's Go Pikachu, Pokemon Let's Go Eevee, Pokemon Quest.
-June: Fortnite, Paladins, Daemon X Machina, Xenoblade Chronicles 2 DLC, Fire Emblem: Three Houses, Overcooked 2, Killer Queen Black, Dragon Ball FighterZ, Starlink, Fifa 19..
Offcourse they could show more staffs at E3 if they wanted, but they didnt want that, and we can expect at least 2-3 more Directs in rest of year where we will have more 2018. announcements.
But that doesn't take away from what i said: Nintendo clearly thought it could use a major game at E3 and get away with it.
It worked. So why not do again? Of, course they haven't been as focused (on a single game) as before, for the obvious reason.
Thing is, this time, people obviously expected more (it's a new console in it's second year already).
Of course Nintendo could show more, as could MS, Sony and other companies.
I don't know how many Indies MS is getting, but i bet it's not 2-3. They could have also showed more, too.
The difference here is that it's clear Nintendo does not have enough to do what the other do - see MS, for exemple.
So, their strategy can't be reveal all that at E3 and then scatter those many throughout the year during NDs. And because of that, they create less impact.
Are you expecting regular NDs or specific NDs?
If it's specfic, like last year, then i agree. One for Smash, one for Pokémon and another specific ND; If it's your regular ND, i don't see that happening. If you look at last year - as an exemple - they only had 1 regular ND after E3. The rest was directed towards specific games coming out in 2017.