We've all seen our fair share of Snoke Theories: Snoke is Darth Plagueis, Snoke is Ezra Bridger, Snoke is Dark Helmet's third cousin twice removed, etc. And a lot of Star Wars fans are eagerly awaiting each new entry of the Sequel Trilogy, desperate to see if their theories will be confirmed in blaze of glory, or crash harder than a Star Destroyer in a Jakku desert.
In this regard, I think fans will be disappointed in the Sequel Trilogy. I don't think we will learn a lot, if anything, about Snoke's origins in The Last Jedi or Episode IX.
This line of thinking was inspired by
comments Rian Johnson made to Entertainment Weekly:
“Similar to Rey’s parentage, Snoke is here to serve a function in the story. And a story is not a Wikipedia page,” the filmmaker says. “For example, in the original trilogy, we didn’t know anything about the Emperor except what Luke knew about him, that he’s the evil guy behind Vader. Then in the prequels, you knew everything about Palpatine because his rise to power was the story.”
In The Last Jedi, Johnson says, “we’ll learn exactly as much about Snoke as we need to.”
Snoke's origins have no relevance to the immediate plot of the sequels. As such, we will not learn about them in the movies. Screenwriting 101: don't bog down your script with unnecessary information.
We have to remember, these movies aren't being made exclusively for obsessive Star Wars fans. They're being made for the widest possible audience. All the casual moviegoer needs to know is that Snoke's the badguy.
Now, that's not to say we'll never learn who he is and where he comes from. But there's no place for that in the movie because, again, it has no effect on the plot. It's something that only us hardcore, lore-obsessed fans care about. If I had to guess, we'll learn about Snoke's background in some comic or novel that will be published after Episode IX (or, maybe, before its release as part of a "Journey to Episode IX" kinda deal).
I think this could very well disappoint and frustrate some fans, but I think it makes sense, and it would probably be a wise decision from the powers-at-be at Lucasfilm.