Most CS conferences serve as publication venues and can't be cancelled or postponed. So how do we virtualize a conference? The ACM has an evolving virtual conferences best practices guide. Putting the talks and poster sessions online is not trivial, but relatively straightforward. Personally I go to conferences mostly not for the talks but for the interactions with other participants--the receptions, meal time and just hanging in the hallways. The ACM document describes some approaches like Dagstuhl-style randomized virtual dinner tables. The IEEE VR conference tried virtual reality through Mozilla hubs. None of these can truly replicate the on-site experience.
Let me mention two other meetings the Game Theory Congress held every four years due to be held in Budapest and the CRA Snowbird Conference, a meeting of CS department chairs and computing leadership, held every other summer in Utah. Both meetings are not archival publications venues though have several talks and panels. But the main purpose of both is mostly to bring people together, game theorists and CS leaders. I hope they postpone rather than virtualize these meetings. Rather get together a year late than pretend to get together now.