Why is everyone expecting a celebration again?
It is impossible for them to bring everyone together in one place, otherwise they would have done it for the PWC.
This is like the time people made theories Goh lied about Project Mew and that he secretly went to invite all of Ash's companions to the finals lol. It is just fanfiction-tier wishful thinking.
I mean Lucario was also fanfiction-tier. A celebration party would be much more realistic than all of them showing up for the PWC Masters 8, as that thing lasted for one week or so in pokemon time, and for about 17 episodes iirc, compared to Ash's friends being in Pallet Town for one or two days.
Either way, looks like nothing will happen but its still really disappointing, especially compared to Alola where all of his classmates, as well as even Oak and his mom, were there to support Ash, meanwhile in Journeys we were afraid for a brief period that NO ONE would be in Ash's corner in the biggest battle of his life