If true that they were still selling dev kits last month with no warning to them that this was going to happen, that is shocking.
However, on September 20th 2018, Sony announced that the Vita was going to be discontinued in 2019, so this quote is a bit weird:
Vita not being made anymore around the time Sir Eatsalot was released, it was inevitable the store would be shutting down sooner or later - like the Nintendo eShop has been discontinued in certain countries for 3DS and the Wii U, and will likely shut down fully in a few years time for those consoles. 3DS was discontinued in the second half of last year and I'm sure is still getting a lot of purchases in the store.
As both a Vita and PS3 owner, the network and stores are a complete mess and the shutdown doesn't surprise me. Really wish the handheld effort went better as I did enjoy the games I played on there as well as Remote Play. Had horrendous drift though.