Multiple companies had already pulled out of the annual conferring of game developers.
http://www.nintendoworldreport.com/news/53054/game-developers-conference-postponed-due-to-covid-19-plans-to-run-in-summer
After more than a week of high profile speaker cancellations due to the Covid-19/Coronavirus, the annual Game Developers Conference has been officially postponed.
Originally slated for March 16-20 in San Francisco, the event was in doubt following companies such as Electronic Arts, Sony, Microsoft, and Epic Games cancelling their appearances in recent days. San Francisco, which hosts the conference, has also declared a state of emergency in response to the potential damage caused by the outbreak. Tentatively, the organizing committee is aiming to hold an event in the summer and is arranging for some presentations to be posted online, and will be processing refunds for the attendees who paid.
Nintendo had not cancelled their appearance at the conference before the postponement. They have had information sessions focusing on Switch development at the show for the last few years, with a particular focus on independent developers.