So with this patch, Blizzard is clearly doubling down on giving every character their own "home map", whether it's a normal map or an arena map.
There's still several characters that don't have a map, and one map that represents 2 characters, as well as a few owner-less maps.
I think that there's a few things that will allow us to speculate on what maps might be coming next, more so than characters, but there's still some cool tidbits we might be able to see in regards to heroes.
Here's an overview of all the characters that have maps associated with them:
Genji - Hanamura or Nepal
McCree - Route 66
Pharah - Temple of Anubis
Reaper - Hollywood(?)
Sombra - Castillo
Tracer - King's Row
Bastion - Black Forest
Hanzo - Hanamura
Mei - Ecopoint: Antarctica
Orisa - Numbani
Reinhardt - Eichenwalde
Winston - Watchpoint: Gibraltar
Zarya - Volskaya Industries
Ana - Necropolis
Zenyatta - Nepal
And as a maybe:
Soldier 76 - Dorado? (I'll get to that in a moment)
That leaves no home maps for: Junkrat, Torbjörn, Widowmaker, DVa, Roadhog, Mercy, Symmetra and Lucio (Estádio das Rãs for Lucioball is in Brazil, but I doubt it counts).
As well as the owner-less maps of: Ilios, Lijiang Tower, Oasis and possibly Dorado. I believe that CTF variations do not count, since they're just repeats of their Control counterparts, just during different times of day and with additional rooms replacing the dropships.
Genji can be associated with 2 maps, and I believe that we might get an arena variation of Hanamura or Nepal - Genji studied there under Zenyatta - in the next arena map release. This I am fairly certain on because the other maps that had 2 characters "owning" them, Anubis and Eichenwalde, got us Necropolis and Black Forest (which Jeff confirmed to be near where The Last Bastion took place). If we get Doomfist, we also are probably going to get a second map located in Numbani or maybe Nigeria.
Which leads us to Castillo. This is clearly meant to be Sombra's home turf, which opens up Dorado as a home map for someone else. Soldier 76's short took place in Dorado, which might indicate that Blizzard considers it 76's home map, however, it might also indicate that we are going to get another Mexican character (Guillermo Portero or someone working for him/Lumerico perhaps? Or someone from Los Muertos?).
We're also likely going to get maps taking place in France, India, Australia (2 here, one for each), Korea, Brazil, one or two in the US, Sweden (I think that the story of the comics has taken us there recently is no coincidence), and Switzerland (likewise I believe that Mercy being from the country in which the ruins of the former Overwatch HQ located is no coincidence either!).
Also, the question arises: Will we keep "ownerless" maps? Because if not, we can expect a second Chinese character related to astronomy, an Iraqi character from Oasis, a Greek character, possibly a second Mexican (as mentioned), as well as another US-American character who has ties to show business, unless Hollywood is considered by Blizzard to be the Blizzard map, which it may be.
Either way, based on the arena maps, I think that if we get another set of 3 arena maps in the future, the next batch likely will consist of Hanamura/Nepal, and two out of Australia, USA and Numbani/Nigeria, which also means that Doomfist or an Australia map might be on the horizon.
Just some thoughts I had.
Edit: Apparently Reaper is from Los Angeles, meaning that Hollywood may be his home map after all. Huh.
There doesn't seem to be any lore connection to them, and Reaper doesn't have any voice lines on Hollywood either, but the location would be right at least.