Ingo Most Likely Hasn't Been In Hisui More Than 5 Years And Will Return Home Because...

Ingo most likely hasn't been in Hisui more than 5 years and will return home because...

Ingo's case ain't like Looker+Anabel. Neither remember anything, show little overall concern about their past, and had their pokemon partners with the. Ingo still has some memories, yearns for them openly, and does not have his team. This is why I feel Ingo was pulled through by Volo, seeing as he is ever so slightly different from the actually established Ultra Wormhole fallers. ALSO NOTE both Looker and Anabel have no known family or deep friendships prior to their fall. Keep this in mind for point 3.

Ingo and Emmet are VERY popular in the Japanese fandom. They will almost certainly include Submas in the BW remakes, especially since the subway system is so integral in general.

Correct me if I'm wrong, but I don't believe main-line Pokemon games have ever permanently separated established family characters outside of pre-story shenanigans. Family and friends are extremely important in Pokemon, to separate popular pre-established twin characters from a game all about duality would be go against all of that.

Ingo's clothes would not survive 10 years in the Hisuin wilderness. Sun bleaching happens VERY FAST in all actuality. Considering Ingo is constantly outside and active, I'd give it at anywhere between 1 to 5 years.

Ingo shows desire to unearth his memories and return home ('strive to find where he belongs' or something of that sort, said during one of his special challenges). I doubt he'd still hold on so tightly if 10+ years had passed. He seems open to leaving Hisui behind, which is easier to do at 5 years than 10.

XX could stand for 20 or 01. Using XX is not only aesthetically pleasing but also avoids giving away any spoilers. Because if they only used one X that would immediately give away the time spent in Hisui. This is the kind of situation where answering one part of the question with a negative spoiles the whole answer.

Irida introduces Ingo to the protag as 'like you[protag]' and immediately talks about his showing up from nowhere with no memories. This aligns him with the protag in their Outsider status, regardless of being a Pearl Warden. Similarly-

The rift in Hisui is recent. While this isn't the first rift to happen, something we are told by the worldly traveler professor Laventon, it hasn't been there for any more than two years. This is because the Galaxy Team and Jubilife Village has only existed in Hisui for 2 years! The way Kamado reacts to it is one of someone starting a new life in a new place only for a very sudden problem to pop up. I doubt they would have chosen to settle there had the rift already existed.

The Clans make no mention of multiple rifts, only multiple distortion spaces.

Post-game, the only NPC to mention Ingo does so by wondering where he's from, drawing attention on Ingo's missing home.

Conclusion: Until proven otherwise, there is far more in favor of Ingo returning home than not.