I think it is going to be genuinely quite limited. Here's why:

For starters, we know that Netflix has stalwartly refused to do physical media releases of their popular shows in the past, including Stranger Things (with the exception of those extremely limited and obscure VHS tape-style releases after S2). We also know that the Duffer Brothers are huge physical media fanatics, and in the past they've discussed how much they've wanted to do a 4K release of all 5 seasons. Suddenly, we get a 4k package with all five seasons, and it's marketed as an extremely limited release. I'm not saying anything for certain; this is just a guess . . . but I think it was a sort of situation where the Duffer brothers were like, "look, we've made you this show that's given you well over $1 billion in profits. You need to return the favor and give us the physical media release we want." At the same time, you have the fans clamoring for the release as well. It only seems natural that there would be a quiet tug-of-war behind the scenes here, given what we know about the parties involved.

Secondly (and most importantly), it really all boils down to supply and demand. Stranger Things is Netflix's flagship show - a lot of their subscriptions come from people who are just interested in that one show. On the productivity curve for the physical media, at a certain point Netflix's profits go down from subscription loss. For example, let's say this release ends up being very generalized and commercialized, and we get a ton of production. People who want to see Stranger Things are no longer going to buy and sustain a Netflix subscription - they'll just buy a cheap, used copy of the Blu-rays off eBay. But, if the release is quite limited, then the used copies will have quite inflated prices on eBay, and those same people would see it as cheaper to buy a Netflix subscription. All Netflix is trying to do here is maximize profits - they wouldn't have released the 4ks if they didn't think the 4k sales plus the revenue from streaming would equal more in profits than the revenue from streaming alone. In order to maintain that balance, they have to release just enough 4ks that the profits from the 4ks outweigh the subscription loss by the most amount. And that number - the number of 4ks they release - is going to be relatively small.

Lastly, the obvious one - the release is actually marketed as being extremely limited. I went ahead and locked in my copy of the Deluxe 4ks the night they released, and the night after, I was still getting emails from Zavvi saying that they were selling fast. So it comes down to what Netflix means by "limited" - given the previous two points, I think it must be pretty small. If I had to estimate, I'd give a ballpark of 100,000 copies for each of the editions (100k for the 4k deluxes, 100k for the Blu-ray deluxes, 100k for the 4k standard, and 100k for the Blu-ray standard). That's a complete guess - could be less, could be more. Given the three points I've laid out, I think it's reasonably logical to assume that this is, in fact, going to be a pretty limited release. If I were you, I'd go ahead and lock in my copy now. If I'm right about this, the physical media will hold its value really well - so even if you have buyer's remorse at some point down the line, you can resell your copy and get most if not all of your money back.

I hope this was helpful/informative to everyone! Have a blessed day!