Guides won't come out quick. Japanese wiki's pop up quick but that's just for completion list stuff so you will still need to look up a proper English FAQ if you want to follow the story. The story should remain the same since it looks like Kiwami 2 uses 2's cinematics as a base, so finding an English PS2 playthrough will let you follow the story. I'm also hopeful that Youtube user Salty Yen will do another playthrough on Youtube or Twitch (Sega is incredibly sensitive about story stuff being shown on Youtube around release). He translates as he plays, not as good as an official translation as his English isn't as good, but he offers some interesting insights regarding Japanese trivia in the games (such as the food you can eat, side stories, to trivia about the wrestlers that appear in the games).
Technically though 2 is loved mainly due to its main baddie. Some plot points are set into motion on this one but nothing that you can't quickly catch up from in 3 or 4 via catch up vids. If you can emulate 2 via PC (pr just play it on a PS2) that's your best bet to play it right now. The game works well via emulation and it'll let you experience the story and fights in real time, which is 100% better than watching a recap vid or lets play on Youtube. The game still plays fine today, especially via PC since load times between fights are eliminated, the controls, fighting etc. are superior to 1's in a great many ways. Lock on is way tighter, tons of heat moves were added and the fighting feels overall refined. There is a ton of stuff to unlock in terms of your character/fighting style (especially if your aiming to fight the Amon Clan).
Otherwise you could just skip to 3, 4 or 5 and just watch recaps of the other games. I'd recommend against skipping any games, just because I love them all and each have their strong points. Assuming your not looking to start 6 as soon as its released just take your time and work through each game at your own pace. Stories are 20ish hours each apart from 5 which is probably closer to 30 (focusing only on story) since its so darn big (add an extra 100 hours onto that if your going for the 100%!). However you could technically catch 2 and 3 in catch ups and then do story runs on 4 and 5 to be pretty caught up to 6 if you want to play 6 at launch.
Hope that makes sense!
On your other points:
Kiwami 2 has no English announcement yet, and with 6 coming in March I doubt it'll be released in the first half of the year. Probably the later half of the year (August maybe?) so you'll probably be waiting a while for any Kiwami 2 English release. I'm doubting we'll get any remaster announcements until at least September next year (Tokyo Game Show) since the team always announces new Yakuza stuff around this time and to a Japanese audience (so don't expect anything from E3). Also, I'm guessing any big new Yakuza announcement game wise next year will be for a brand new chapter in the series that takes place after 6, staring the new character Ichiban as they've revealed the new main character and that a new console game is coming, but that's it. Any remasters are probably fairly way down the list, so I wouldn't hold out hope for those coming any time soon!