I think it's more that they are releasing more or less a "definitive edition" in the coming months, and it's entirely separate from the current DS2. AND the current DS2 will NOT be updated to include ALL of the new content, only *some*.
Like right now I'm busy stealing a bunch of lvl 3 key spheres from Biran and Yenke before forcing them to do blue magic so I can learn all of that.
Just one more and I'll be satisfied with moving on.
Glad I used Kimahri over Auron, they aren't posing a threat at all.
I always took my time on that fight as well (Biran/Yenke).
The way I play FFX is I swap every character into every battle, so they all grow equally. Even if you just swap someone in and just defend, they still get credit and AP. Yes, it takes a bit more time to progress, but it's well worth it in the long run.