Because the sets are going to be likely to be piecemealed up and what we get is pure speculation. Maybe I didn't make it clear enough in my post, but basically we can't really be sure what we're going to get in our May set. Our May set could be part the last part of Psycho Drive/Hail Blizzard and a bunch of promos similar to what CoL was. It could also contain most of Dark Rush/Selection's.
Because of that uncertainty it was impossible for me to judge the set based on what we know since any of the cards could be thrown around in some random order. What we do know though, is that all the cards will definitely be available after worlds. Hence that was the best objective benchmark for me to judge them by. I didn't mean to make it sound like I was speculating what we were getting in May, simply trying to use the best benchmark possible for discussion.
I can understand your reasoning for using post-Worlds to judge the cards, I appreciate the explanation.
Still though, I recognize it's speculation, but generally we can make pretty good assumptions as to what future sets will contain, using past experience and trends. Let me explain my logic:
We got some HB/PD cards in our NVs set (~14, from my quick counting). Not many, but a couple, plus we got all of Red Collection. So, that leaves the rest of HB/PD, the Reshiram EX/Zekrom EX decks, and Dark Rush.
We know there are 99 cards in Next Destinies. There are about 90, not including secret rares or full arts, cards from PD/HB that we do not have yet. With the SRs and FAs it's about 100. So, in theory, we will be getting most of PD/HB, with maybe a handful of cards (no more than 10 or 15) held back. That leaves us with about 20 cards from the EX decks, plus, let's judge on the high end, 20 cards from PD/HB we won't have after Next Destinies.
There are 69 cards in Dark Rush. Add 40 to that, we get 109, a good number for a set. So, maybe we won't get much of Dragon Selection in our May set, or maybe we will. Regardless, I feel safe in saying we will indeed get much of if not all of Dark Rush in May.