Hello everyone, there are some things that suggest Kalos and Unova are connected via train.
According to BW and BW2, in Anville Town, the train is being worked on to be used in the future. It is said to be undergoing a lot of testing and can run on any rail. The brown track also breaks off into 2 tracks and continues north.
I have seen some text that says, "Those cars no longer run in the Battle Subway, but I hear they run in a far away region." However, I can not find this in the games.
The maps of Kalos and Unova could also mesh together well. This is speculation based on what I have recently seen. You may ask why Unova wasn't in XY if it was in lets just say Z for now. Simply put, they just didn't have time to make Unova 3D. In the pre release pictures, you could tell they really wanted to make Unova like Kalos, but it fell short. The traine being worked on in Anville Town could be what would connect Kalos and Unova, but it just wasn't ready yet at the time of XY. This may explain why Ash had to take a plane instead in the anime.
Kalos was already being worked on when Unova came out. That was basically stated in the game in Castelia City at the Game Freak HQ. We also have a few French people scattered around Unova. Although Kalos has a lot of connection with a good amount of the games, Unova seems to be the prime. This could also be why we haven't gotten many 5th Gen megas at all, when we have gotten Sixth Gen already.
We have an unused train in Kalos and we have a train being worked on in Unova that will be used in the future. Not to mention Kalos and Unova are show similar traits to New York and France. And Kalos and Unova share a lot of history as I have said before.
Yes France and New York are across the ocean from each other, but Masuda did say not to look at the the pokemon world as our own, because it would limit them. Kalos and Unova could be a whole new continent and close together like Kanto, Johto, Hoenn, and Sinnoh are. That would explain why Unova had so many pokemon.
You could also say it is unlikely because both regions are surrounded by the ocean. However, Undela is a bay, which means it is surrendered by land. Kalos as room south and east. Unova has room north and north east and north west. They could still have South Kalos, but still connect to Unova.
However the routes do not connect as both start with Route 1's so this could be the indicate that all of the above is wrong. This is all just speculation and a ton of hopeful wishing. I am not confirming anything.
My main focus here is the train being worked on in Anville Town that is said to be used in the future. Which I am extremely surprised no one had brought that up, at least not from what I have read. It is also possible all of this has been said before.