[Boudica]

You know what... I don't think they'll do much damage to Netflix. When Disney+ launched a lot of people said they would leave Netflix, and some probably did but most people I know, just kept it and bought Disney+, same with Prime Video, when good shows came up, they just subscribed to Prime and figured shit, I use Amazon anyway.... I've been a prime member for years and I don't think I've watch more than maybe 30 minutes of Prime video. That's not to say there isn't good stuff on there, but the good stuff you gotta subscribe to Starz or whatever and it's a drag. I'm going to assume since they said 8B, these will actually be part of prime video. This is all opinion, the numbers seem to show a decline so you may be right

Most people that are subscribed to Prime, are probably using Amazon's other services. The MGM titles will just be icing on the cake for people that already use Prime. Little things add up, but I don't think Amazon or Disney+ are doing direct damage. Netflix is also raising their prices and targeting account sharing. Over time Netflix could be seen as less desirable, especially when IPs like Marvel and Star Wars are going elsewhere.

Netflix has always had different fees over the numbers of people who can share screens. Several other services do that too.

I think Amazon Prime is a very different business model to the other streaming platforms. E.g. Amazon firestick. My family use that over a regular TV box. They also have prime but probably 90% of what they watch isn't through prime video because the selection is naff. They probably have the worst selection for the things my family watch day to day. However, they definitely have great older movies (which come and go from being free on prime or not). They also have options to easily buy and keep films that aren't already free. The same cannot be said for Netflix, as once you have paid for Netflix, you have access to the full catalogue. The only extras you can pay for, are multiple screens.

Long story short, these platforms work differently, and target different audiences. Netflix provides their full catalogue and only charges for extra screens watching simultaneously. In the space of 10 years, my family (5 users) have only had an issue with this once.
Amazon has multiple methods of making more money. Prime gives more benefits than just Prime Video, you can purchase more films/shows on the prime catalogue that aren't free, and they appear to reach a different target audience.

I'm not sure this is the death of Netflix, given Netflix is growing it's anime section and it's originals seem to be it's biggest money makers.