Considering that this is the year of revealing the PS5, I find it hard to believe, even more so since they were absent last year. Back then I got it, they did not have much to talk about so why organize an event to simply repeat what we already knew. But by E3 2020, there's the PS5 and surely teasers/trailers for the first PS5 games, exclusives etc.
Sony keeping silent during E3 2020 highly unlikely.
Nintendo didn't show Switch at E3, worked out for them
Nothing to see here, move along