In 2017 we knew lot of games announced for the second half of the year before E3. In 2018 we have only Smash Bros., Yoshi and The World Ends with You. I think is high chance for Direct (or Direct mini) before E3 (E3 starts on June 12).

E3.
After the DS delay, I think Nintendo wants to first cool down the fans.

Either way, we basically know 2018 is going to have a killer second half for Nintendo.

2017. was year of release of console so they needed to show more games in January Switch presentation not just games that will be out next few months. Also dont forget that last E3 also we had games announcements at E3 that were released few months later, even after E3 we had September Direct where for instance Doom was announced and released only 2 months later.

Since 2013 we've not had another standard general direct before E3 after getting one in March/April. I expect that to continue so what we'll get is a game specific direct like we usually do (likey for Mario Tennis) and/or a Micro/Mini.

Do we? What is expected besides Smash Bros and old ports?

Fire Emblem. 

And either Animal Crossing or Pokemon. Probably the former.

That is a pretty good lineup.

it feels like they would be getting a bit too close to E3 if they did one now. we have 2 months to wait, which isnt even that long considering we got a Direct only a month ago and people are still riding off of the Smash Bros hype

So May 10th?

Adding to the calendar.

At E3 if there's no Pokemon, a few days before E3 if there is Pokemon, unless Nintendo is really saving the reveal for E3.