Training has always been an important reason for players to visit another area now and then and get to know the whole existing world (even years ago already, when Ojaveda used to be where the Explorer Outpost is now, and there were no more towns at all).
But of course, the more locations in game appear, the more NPCs with similar features as merchants or trainers should exist, especially for the lower stat & skill levels. It is more annoying for beginners to travel longer distances. Once you are trained good enough to solve the Winch quest lines and afford a mount, you possibly already have advanced levels of physical stats too.
I believe when the spawn points of different races will diversify again, then the amount of trainers for specific skill ranges will multiply as well.
