I believe Sal said something about ZDP. I'm too lazy to look through the bombshell thread. If I had to rank the likelihood of steels for the P4 LW, they would look like this: K390, ZDP, and Hap40. As for Hap40, I have no knowledge of this steel making it to the P4 LW, nor have I heard of any rumors claiming this. Hap40 is a popular steel, so I wouldn't be surprised if it made its way to the P4 LW one day. I'm still going to beat the drum for a laminated CoS Seki sprint run — P4 LW included.