1). If you're buying a One S, it does have the benefit of being a cheap UHD media player on top of being a game system. For the most part, it'll get the support from the major pubs. That's why they try to keep it at a competitive price so the big third parties don't second guess about putting content on the platform.
Plus, if you don't own a capable PC, it's always an option for people who really like MS's franchises, but weren't in a hurry to get the console. Xbox also becomes an attractive option due to MS's constant deals for the system. If you're patient, there are times you can get the console with multiple game and gift card giveaways. MS spares no expense to try and get these in homes. It can be a big value for budget gamers.
That being said, if you're buying a console looking for the best specs at this stage of the game, it's time to wait until the Scorpio debut to see which SKU is worth your dough.
2). For exclusives, there's practically no reason for MS to seek out Japanese devs to develop content for Xbox anymore. Even if it's a contracted job, it's not a sure thing. The Japanese buying public has spoken. MS is likely still in the region as a face saving measure. MS gamers in the west will still buy these games if it's a major release, just not nearly as much as PS gamers. If the cost of devving ports for the platform outweighs the projected sales, then that's when it will be an issue.
3). See 1
4). Only playing Xbox games on PC, I couldn't tell you. I do hear they're trying to make improvements to the UI all the time. So I figure one day they'll have it ironed out.
