My prediction for 134 and after:
Goh will get Mew.. Some fans will rage about it... the anime writers wont care.. and the Pokemon anime will just move on.
If younger audiences are happy to see Goh catch amazing and popular pokemon, the anime writers feel they've accomplished something to help build more marketing to support the pokemon franchise.
It seems to me that the Pokemon franchise has reached a threshold that they are wanting to further raising the bar of their marketing by promoting its target main characters (Ash and Goh) to accomplish amazing feasts just to build more positive support for their aging franchise by having said anime protagonist (Ash and Goh) accomplish the said goals they've set out to do towards a new story arc (PWC and Project Mew).
I dont truly care much about Goh since he's essentially a marketing tool to promote the pokemon franchise and is not a character that the writers are bothered to invest their years in building up like Ash. Case and point is the fact that Goh was given a Suicune and was able to catch an Eternatus.
Evenmore, the kid(Goh) has had such a spontaneous development, that he's now become so talented that he can now overpower some legendary pokemon and catch them. Even commenting at one point in promotions that Goh is almost as independent as Ash. Based on this type of story development, it seems writers dont seem to have a long term goal of investing in Goh like they did with Ash.
How I see it if the director and staff team of pokemon journey's didn't have a problem with a newly introduced character (Goh) catching one of the franchises most popular legendaries (Suciune) as a keep-sake, then I dont see why they would object with him catching Mew, espcially seeing how Goh is just a marketing tool to build up more viewership to watch the anime. Doesn't make sense if the "Gotta Catch'em All" poster boy fails at accomplishing one of his grandiose goals to get one of the most renowned mythical pokemon; Mew.
Just imagine the viewer ship with Goh having Mew in his party and traveling around with it. Lost of younger and new audiences would honestly be aroused by this development, and to be honest I would have too as a youth watching the original series if Ash had caught populaar pokemon and legendaries early on such as Zapdos and Dragonite.
To be honest, I cant be mad at the writers for wanting to try something new, especially when they're burnt out recycling the old story formula. If newer fans want to see the older formatted series, they can just re-watch the original series.