The site claims to have gotten their information from sources close to Sony, while another Spanish site in Legion de Jugadores is reporting pretty much the same, also citing sources close to Sony.
This is a pretty big claim, considering where it's coming from. But if it's anything close to true, the aforementioned websites should receive a huge credibility boost. If it's completely false, then, ah well...
To be fair, though, this doesn't seem extremely far fetched (only a bit). Sony will be sitting out E3 this year but dropping such a bombshell ahead of the event could do a bit of damage to the competition.
This rumor comes ahead of Kojima's Death Stranding's reveal too; so it's possible that they're both related and that Sony's planning something huge for State of Play. Who knows?
The Last of Us 2, Death Stranding and Ghost of Tsushima have all prompted much anticipation over the last few years and there were fears that they could launch after the PlayStation 5 drops. However, Sony has confirmed that all three exclusives will remain PS4 titles, which doesn't mean they won't launch for the PS5 but should come a bit sooner than initially feared.
So, while Sony will be skipping E3, they still hold enough cards to bombard fans with major announcements and steal some of the event's thunder.
They've had a huge say in the market with their exclusives recently, with God of War having sold over 10 million copies since its launch last April. This April's exclusive, Days Gone, has already surpassed GoW's lifetime sales in Japan and has been dominating the charts over there, as well as in the US and UK, for weeks.