Full production is expected in a couple of months as per Bill's post. There's already been early production models floating around some Nashville pro's.
The Peavey one looks to be made in Taiwan so I imagine there will be a lot more availability wise. Some people will criticize it being made in Taiwan rather than the states but it's a much better compromise than China in my opinion. An all time favourite of steel guitar reverb, the Boss RV3, was produced there many moons ago and for a lot of people, have been reliable.
For comparison, the TC Furlong one is handmade in the USA and is a one man operation. It took me a while to get mine as the first couple of batches quickly sold out. The Sesh 400 is described by TC as a "faithful tribute".
From what Bill is saying on Facebook, the Peavey one is an exact replica...but time will tell.
Sometimes I think I'm psychic...it was just this afternoon that I was thinking about a couple of old listings on here for Session 400s, that I never bought

Kind Regards, Steven Hicken Jr.
Steels - 2015 Show Pro SD10 - 2025 Resobird - Steven Hicken Sr's 1981 Sho Bud "The Pro-1"
Amps - Quilter 202 TT12, TC Furlong Sesh 400