Diff bomb hasn't been set yet. There was a talk upcoming on 13/05 about whether to set it up now or delay it since record of diff bombs goes off, avg transaction increase and hurt the ETH ecosystem in a short term. Though I do think diff bomb is needed if ETH wants to move from PoW to PoS. This late release of 100% unlock hashrate for nvidia LHR cards feels like a prisoner's last dinner, really. Don't know if it was good news or bad news since ETH diff for now will increase further.