Nintendo won't dedicate a direct to Smash bros, they'll prioritize hyping up games they need to sell over ones they've already sold.
The smart money is on March 30-31st for gameplay/full trailer stuff, premiered at Sega FES. Assuming we're getting FeMC mode, they'll lead with the new version of Persona 5 with FeMC in the event, then have Joker Smash Trailer including FeMC near the tail end when the hype slows down. Might also have gameplay stations. As for actual release date, late april still most likely.