Modified Format for next year?

[Broken Pokemon EX]

Hey guys I only recently got back into the TCG, and most of my cards have been rotated out of format by now. I was wondering how many sets usually get rotated out of format each year because I wanted to play competitively this coming season next year and I just didn't want to stock up on a bunch of HGSS cards if they are going to get rotated out when cities/nationals/worlds/etc. gets crankin up again.

And I apologize if this question has been answered somewhere else, but would anyone have advice on what sets would be a safe bet to start collecting cards from?

 

[DawnOfXatu]

I'm pretty sure this next year will be HGSS-On all the way through Worlds. Although if you are looking for the safest bet for which sets to start collecting from, I'd suggest BW-On as you'll get at least two years out of those cards.

 

[Glace]

Yes. There will be no addition format change after this Worlds. The change to HS was considered just an early rotation.