I took that as a conclusion to the Mishima family feud. Why Heihachi did the things he did, the origin of the Devil gene, etc.
That's pretty much wrapped up now, so they can have a new focus for the next story.
All new characters gets more difficult to do the bigger the roster becomes, and these days the rosters are pretty huge compared to the old days.
I think at that point it may be better to make it a different series and call it something else, kind of like how Garou Mark of the Wolves is different from King of Fighters.
Which kind of ties into DLC. If the roster keeps getting bigger and bigger, and you want to launch each new entry with some new characters, at some point it becomes unreasonable to include every classic character. But it's understandable that people can feel unhappy about that.
But a normal player can't make a player of Gamerbee's caliber eat all those DPs in a row in spite of the great risk it carries if it is blocked. Which is why we never saw that happen again in SF4's lifetime, and why it became a legendary moment.
On the former, kinda my point. Yes, it's great to continue on with your characters but the more they add and the more they want to promote new ones or appeal to a market the more they will also leave behind or more work they create for them. They can adapt however, Lee when added was basically just a Law clone, slightly different moveset but by the time 4 and onwards came about they redefined his kit massively. 6 version of Lee was superb and fluid but I fear he is an outlier character, added only because of the story involved in T7, much to the reason why classic characters Anna, Lei and Julia were left out and added as (paid) DLC only later. In 8 without the Mishima stuff being for front, I feel he will fall out of the game, like Lei did. Meaning my 'mains' are starting to dwindle.
Solution? Don't make Tekken 8. Make something else but the same gameplay. I can't be disappointed in Lee not being in it if no one's mains are in it. They can add characters that have similar fighting styles but with a new game, new gen, why not mix it up with new story and characters as well?
On the latter, more than I know what is capable in Tekken and not SF and MK as I'm not a fluent in it's tactics. But can't deny I don't enjoy the high level play viewing, they are the best of the best for a reason.