For now, it seems that way. But we don't know if the hero talents will be the future 'progression' from expansion to expansion. IE: They slowly expand the additional talent trees so that over-time the differences between each one start to broaden and expand. Think old-school FF job advancements or any kind of eastern game that has evolutions.
I could see it happening, slow and steady additions vs major revamps and squishing everything.
Question is: What is the player power fantasy going to be in the future? We can only add so much onto the current systems before it becomes somewhat redundant / confusing for normal players. Are we going to move onto a Diablo-style horde grinder with a stronger importance on variety and playing the way you want? Are we going to push harder into specific roles more than just dungeon's? Etc. etc.
Delves might answer this question once we see them in action.