Might have been during Japan Expo in France. I don't remember the exact questions from the interview. And, oh yeah, that fact that Takei never said that FnU falls in the SK timeline/universe. So, it still doesn't hold water either way.
And more importantly...
All these theories are great and all, but, you know, they are a bit too Yoh/Hao centered. Takei's finishing off the series, not just that Yoh/Hao bit. He has already stated that there will be a Horohoro-centered chapter in the ending. Which he gets about 10 chapters. So, one of those chapters is already covered. The question then really becomes, what happens in the other 9 (and how Horohoro fits in)?
Logical, character-based chapters are:
5. Sati (with Elemental Spirits) (and Ryu)
6. Redseb/Seryam/Faust (all those dead people)
7. Anna/Manta (and people on the beach)
8. Silva (and rest of Patch)
So yes, the Yoh/Hao plot is important. But when developing theories, remember the cast. Any theory basically needs to start the Yoh/Hao thing, then work in chapters that support a conclusion with all the characters listed. Since Horohoro is confirmed, clearly these others will get their time to shine as well.