Is this episode gonna be part of season 20 or the season 21 premeire? (Mewtwoclone (talk) 20:01, September 27, 2017 (UTC))

Wait for it. If TPCi announces that it will be season 21, then it will be season 21. We are going to list it under the current dub season until another one is announced. Due to the lack of seasons in the original Japanese version (due to them being dub only to the American format), we have to wait for TPCi to announce this to know for sure. We're currently listing it as "(tentative) season 20 [confirmed only in Japan]" with others that don't have dub titles until they are revealed to avoid such speculation.
In the original Japanese version, the episodes are separated by multiple anime shows (as in multiple TV series) that are connected to a single franchise (for this one, Pocket Monsters Diamond & Pearl, Pocket Monsters Best Wishes, then Pocket Monsters XY, then Pocket Monsters XY&Z, then Pocket Monsters Sun & Moon), and may be sub divided into their own arcs - Japanese anime television does not have "seasons" specifically. American television does it differently - they label them by "season [number]" and may sometimes even name the season like how Lab Rats season 4 was named "Lab Rats: Bionic Island". So we don't know just yet - wait until TPCi announces which dub season it will be included in. Until then, we'll list it under the 20th dub season, Sun & Moon.
If TPCi maintains the 20th dub season to have 43 episodes (similar to how season 1, Indigo League had 52 episodes, Orange Islands had 52 episodes, all the Johto seasons had 52 episodes, then the Advanced ones up to Advanced Battle had 52 episodes, then they varied from Battle Frontier when TPCi took over), then this would be the premiere one. This is if you're going by season production and not season arc.
There's a difference between season and arc which is a common mistake among western fans of the franchise that is unfortunately very common. Season productions go up to 52 episodes and are the standard that Poké and international DVD releases use (with the only inconsistency of the three banned episodes in season 2 not recognized on the English Pokémon website, which drops the number to 49). Season arcs are what Viz Media uses based on the opening themes - only Viz Media calls the full arcs seasons, which are a common convenience format including the convenient format we use here (we use Viz Media seasons here), and I don't have any objection to using that here - don't confuse this as me saying I oppose season arcs being listed here, it's actually better if they are since it includes any banned or undubbed episodes that fall between the numbers of any Viz Media or production season - it's just that I personally view the episode numbers by production seasons, and whenever listing "season [number], episode [number]" for dub format in such rare cases, we use production seasons here such as on the specials page, I just want to note the differences between production and arc versions of seasons, in case it needs to be brought up in the future. As of all of TPCi's produced seasons, the season arc and season production have always had the same number.
The same goes for the arcs - just because a new arc is announced in the primary canon of the anime (the original Japanese language version) does not mean that the episodes will belong in a similarly named dub season. We are always going to wait until TPCi announces the 21st dub season because there is a chance that they will do something completely bizarre such as to not dub the remaining Sun & Moon episodes at all ending on season 20 and therefore there wouldn't be a 21st dub season until the next region series so we need official confirmation from The Pokémon Company International before creating a season page, rather than assuming what the next dub season will be based on the original Japanese version.
Edit: To clarify, any announcement from the English speaking official companies such as the broadcasters of the show (Disney XD, CITV) is also accepted as a source to create a page for a dub season, but they must be announced by the official English-speaking companies, with an official title rather than just a wild fan-made guess based on the Japanese version. When the pages for dub seasons 20 and 19 were created, we were assuming the new arc or the new anime show in the Japanese version meant there was also going to be a dub season - but me and the admins have agreed that we cannot afford to make these assumptions, because it is very unlikely but entirely possible that they can choose to do something bizarre and do something to make that assumption wrong - for example, choosing to not dub the series or arc at all, leaving it with no dub season. Even so, we shouldn't have made the pages under fan made names like "Pokémon: XY & Z" or "Pokémon: Sun and Moon" - the naming should be waited on until they have official names. PokémonGamer* 01:35, September 28, 2017 (UTC)
Update: Season 20 is announced to have ended with SM043. We're still unaware of what the 21st season might be called, but whatever it is will likely include this as its premiere. PokémonGamer* 05:33, December 23, 2017 (UTC)
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