Tough to say. On the handheld front, Nintendo did this with DSi and New 3DS. I think it helped in those cases. The DSi in particular was a success because it added a camera and a digital games (DSiWare) store. But I think those platforms would've continued to sell regardless, so a mid-gen specs boost wasn't needed.
The PS4 Pro is basically the best 1080p console on the market. Even if you have a 4K TV, the resolution is dynamic in a lot of games. Sony dropped the ball not including a 4K Blu-ray drive. If the Xbox One S can have a 4K Blu-ray drive and be very affordable, so can PlayStation. Xbox One X delivers a much better (though not uncompromised) 4K experience. The Xbox One X did not seem to help Xbox One much besides adding 5-7 million more units sold, and the bragging rights of the most powerful console on the market.
I suppose the answer to whether or not mid-gen upgrades would be helpful for the Series X and PS5 are very much up for debate. We'll have to see what developers can squeeze out of the consoles during their lifetimes. Let's just say a game like GTA V would've been pretty unthinkable on the Xbox 360 and PS3 at launch, yet they made them work in 2013.
Circling back to Nintendo, there are debates of whether or not Switch will get a "New" or "Pro" version. If Switch 2 doesn't come out until 2024, I'm very sure they will. But if it's out in 2023, that makes it less likely. The Switch is selling very well, and developers have squeezed some impressive games out despite the spec limitations. I have a feeling a mid-gen Switch update would be more akin to a PS4 to PS4 Pro leap, not an Xbox One to Xbox One X leap.
I guess Sony didn`t put a 4k BD player on the console to first not canibalize their standalone player, second because there aren`t much 4k BDs in several markets and third well hardcopy movie have shrinked much more than console. So yes it is good that it is even on X1S, but Sony probably saw it would only ad costs but no revenue to them.
duduspace11 "Well, since we are estimating costs, Pokemon Red/Blue did cost Nintendo about $50m to make back in 1996"
Mr Puggsly: "Hehe, I said good profit. You said big profit. Frankly, not losing money is what I meant by good. Don't get hung up on semantics"
Azzanation: "PS5 wouldn't sold out at launch without scalpers."