Veiler and Maxx C will probably lose popularity in the main deck too, which is good for karakuri. VS Darkworld you can pretty much always guarantee a first turn Naturia Beast if you have the right cards for it.
Okay? Thats like saying. You can pretty much first turn exodia if you have the right cards for it. The problem is getting the cards and getting around stuff that stops us from doing that like Rai-oh. With all the TGU crap(acid golem, zenmaines,etc) and agents. I highly doubt veiler will becoming out main deck any time soon. Same with Maxx "C"
1. The comparison with Exodia only holds in the sense that they are both unopposed. However, comparing the probability of opening Exodia and opening with this 2-card combo makes no sense. You only need Komachi in hand + Merchant/Cash Cache to get this combo, which is what makes it extremely easy. The only other deck that can easily produce this first turn Naturia Beast is Samurai with Elder/Kagemusha + Asceticism, or Dojo plays.
2. Rai-Oh is irrelevant, since my post was about first-turn Naturia Beast, and I do mean when you win the die roll and it is the first turn of the match. Furthermore, Rai-Oh's popularity in the main-deck is dependent on how the meta shapes up. Regardless, my post was not about how to handle second-turn openings. That's another topic.
3. As far as Veiler/Maxx C losing popularity, it may or may not be the case that they do. It really depends on how the meta shapes up to be, and what other exclusives are revealed. Which is why I said "probably".
4. Furthermore, I was mostly talking about the Darkworld matchup, if you read my sentence. In the darkworld matchup, Naturia Beast is key if it happens before Grapha is in the grave, and it is unlikely that you will get hit by Veiler (space is tight in that deck, and Veiler being in the main is not guaranteed). If the spells are cut off, you only have 2 worries: Grapha in hand and TGU, but for those there are plenty of solutions - Fiendish Chain, Solemn Warning, Bottomless Trap Hole, Book of Moon, Enemy Controller.