Here's what I think will happen: Castle Siege will be used for Genesis 6 and maybe Frostbite and then the top level TOs and top level players will conclude that it's a banned stage and they'll ban it. It'll stay banned from then on.
Unova will likely end up banned eventually as well. Yoshi's Story might too (similar to Battlefield). My main hope is that Lylat makes it out alive.
I hope you're wrong, but I certainly understand the reasoning for the prediction. However, I believe the inclusion of Castle Siege, Lylat Cruise, Yoshi's Story, and Unova at a super major like Genesis shows evidence that the top TO's are not as conservative as many thought.
I don't believe a similarity of platform layout is enough to ban Yoshi's Story (YS) and/or Unova. Years of Melee competition proves that differences in stage-base shape and size, blastzone sizes, and platform placement are all enough to heavily influence a match-up. And that's with
FOUR triplat variants, lol. Platform similarity as a ban-justification simply does
not hold up if the stages have enough differences. To map these out for everyone, I've included the numbers and other notable difference below for BF/YS and PS2/Unova below
Battlefield/Yoshi's Story comparisons:
-Stage bases: 160/136
-Side blastzones (bz): 240/227
-Top bz: 192/180
-Bottom bz: 140/118
-YS offers distinctly different ledge play due to the slanted edges, platforms that reach all the way to ledge, base that goes straight down for wall-jumping, and very shallow bottom bz which allows early spike kills and pressures players to think twice about recovering low too often.
-YS's stage base is a whopping 24 units smaller than BF's, so heavies/slow characters that like the triplat layout will
MUCH prefer to go here.
PS2/Unova comparisons:
-Stage bases: 188/164
-Side bz: 250/237
-Top bz: 180/190
-Bottom bz: 125/142
-Unova has distinctly different ledge play due to the walls that go all the way down, platforms are noticeably closer to ledge, and the bottom bz is much deeper which allows wall-jump characters to recover much lower than on PS2. Players can also DI in when spiked close to the wall with great chance of catching a tech and saving themselves due to aforementioned points.
-Hard blows on Unova will kill later off the top and earlier off the sides, a deciding factor depending on how the opponent's character kills most consistently.
-Unova's stage base is a whopping 24 units smaller than PS2's, so heavies/slow characters that like the biplat layout will
MUCH prefer to go here (seeing a trend?)
As for Castle Siege (CS), we again have to go back to the point that players need to be more
open-minded to change and TO's need to be mindful of keeping the stage list
balanced with a fair amount of
small, average, and
wide stages. If we lose CS, we lose a greatly needed small stage. To ensure balance, any stage list should have
AT LEAST 3 small stages. You can't please everyone, so pleasing people by removing a stage that's a tad-bit controversial (even though it shouldn't be) should
NOT be a priority. Balancing the stage list to ensure the healthiest meta, however,
SHOULD be a priority. If TO's want to remove CS in favor of Warioware, I'm all for it. Problem is though, you'll have other people criticize that decision for different reasons. Which goes back to the TO's "
can't please everyone" statement, so, tbh, they need to stick to their guns, keep 3 small stages in the list (idc which 3), and
set this game's meta up right from the start. 
