This decision was officially unveiled today, via official QuakeCon Twitter statement. There, they say that the ongoing COVID-19 outbreak brings a lot of logistical challenges and uncertainties. And ultimately, that after a lot of discussions, that decided to cancel the event.
QuakeCon 2020 was planned to be held in August, as is tradition, which seems quite far away from the current crisis, but as is stated in the announcement, it's hard to plan things in the current state the world is in, and the health of all involved is a top priority.
It's a shame that another big event got cancelled, QuakeCon was always a place to discover new great stuff from Bethesda Studios. But, at this point, we can expect all the major events this year to be either cancelled or postponed.
You can read the full statement below: