I don't want all the regions to be connected. The only way to get to them all would be by plane. Hoenn is far away from both Kanto/Johto, Sinnoh is north of Kanto/Johto making it a big distance from Hoenn, and Isshu will more than likely be in somewhere around Hoenn or Sinnoh but not close enough that you could easily commute. It would be nice if we saw at most 3 regions connected (Hoenn, Sinnoh, Isshu), yet for some reason having all regions connected wouldn't make the games any more fun than they already are. It could get boring doing the same thing in each region if there wasn't a different storyline to follow in each, and if say you didn't restart with a new team (though could use old too) in each new region with their respective starters.
Regardless of all of this, it just won't happen. That would be the perfect way to ensure people don't buy more pokemon games.