This could rise like HZD did and TLOU2 could slow down quite a bit yet, I know you don't like to hear it but the casuals have spoken on that one and they hold the true selling power, we are ants compared to them.
Horizon sold 10M; this game can do it too. I doubt TLOU2 reaches 10M
I wasn't near as hyped for TLOU2, but more so because I had already assumed it would be undeniably the best of the gen hands down. Even with everything that's going on with that game itself, it could still certainly hit 10M, though it won't be as easy as it could have been on it's own. I wouldn't be surprised one bit if TLOU2 get's bundled with PS4 this holiday or even PS5 eventually, which will help to boost overall sales.
I agree, as I get the feeling GoT is going to have legs based on what I'm seeing. It could very well end up slowly catching on and rising to heights like HZD did. If it's properly enhanced on PS5, that could really give it a major boost.