I don't see why we can't still get a Spec 2.0 update with GT6, just not this month...
It seems that there's still a lot left to do with GT6, considering a few major planned features still haven't been added. And Kaz made comments about the course creator being "in beta" - it wouldn't make sense to say that to the public and then cancel it's release without a formal notification. I could see the either final few features being added in a "blowout"-style Spec 2.0 update, or after all of the previously-planned stuff gets in, Spec 2.0 will come in introducing all sorts of stuff outside of the promised-update content, similar to GT5. It doesn't necessarily have to fall under the anniversary month.
Also, if I'm not mistaken, wasn't it mentioned at the Ask Me Anything (or some other panel) at Playstation Experience that there was a decent amount of content still due for GT6, including a track or two? Or was all of the commentary relating to GT7?
I think a large batch of content and/or Spec 2.0 is still gonna happen, just not now, or perhaps a in few updates.