I have two thoughts, and in gonna lay them out back to back in one post, because I'm a wild man.
RE Japanese studios and games. Just because we aren't seeing ports yet doesn't mean they aren't in the works. These things can take a minute, longer depending on the studio. Especially if the ps4, PC, or switch versions were already in the works when the deal was made. I hope we see Xbox return to TGS soon, that would really be a show of confidence and commitment to me.
That being said It doesn't really seem like ports are Xboxs focus though, I think they're more concerned with bringing games to the west that wouldn't have made the jump before. Which will probably help in the long run. If these games are successful on Xbox in the west without first being successful on PS4, it shows there's an appetite and it might be easier to convince Japanese developers to aim at Xbox from the beginning. That combined with building support teams in Japan tells me they're playing a long game.
RE XCloud and "forward compatibility". I'm beginning to think more and more that, at least early in the gen, Scarlett games will be supported by Xbox One X at least. Obviously scaled back versions and it won't be universal, but I think it'll be pretty common. The reason I think that is because we know X-Cloud is currently being built with Xbox One hardware, and they're saying it will play "four generations of Xbox games". So either they're gonna have to immediately replace and augment the Xbox One fleet with Scarlett units once specs are finalized, and won't be able to stream any next gen games until the rollout is done, or Xbox One will be able to play Scarlett games at least for a few years so they have time to roll out and QA the Scarlett streaming fleet and eventually cut over from the Xbox One fleet.