Maybe not, but I'd say there's still a lot of it floating around the secondary market. I mean, you can still buy an unopened crate of WWII vintage rifles for relative peanuts, I imagine that mass-produced armour either commercial or ex-police is likewise in abundance. If someone wanted dirt cheap body armour, then Type I is going to be better than nothing and cost virtually nothing. If we are talking about sound investment in protection, then yeah Type II minimum, maybe Type III-A depending on your local area, but at the end of the day, these are low-intensity protection not intended for a tactical situation (where Type III is now standard).
So it makes sense that the SMG is falling out of favour in that range of applications, but I still think it has a niche that can't be filled with an SBR. Outside of the hypothetical future as a full retard home defense solution, the SMG has transitioned into the PDW which takes the small profile and good handling of an SMG (down to 6mm or so) but has it designed as a downsized rifle cartridge for better ballistic performance that one generally associates with an SBR/Carbine. The obvious issue is stoppan powah, but tbh death by 1 full size round is the same level of dead as 2 smaller ones, so a high cycle-rate PDW does the job fine.