We know the series was originally scoped to be much smaller, from the ol' Russian leaks back before/when the game launched. Game 1 was roughly as we saw, Game 2 had 3 core factions (no Skaven), and game 3 focused exclusively on the four Chaos gods' factions. Presumably there was the same idea of a 'combined campaign' for each game, but the success of 1 and now 2 has led to them dramatically widening their development roadmap.
In the original plan, there was no Norsca or Vampire Coast DLCs. Game 2 was sized more like an expansion pack (with 3 factions vs. Game 1's 5), and Game 3 was presumably a similar scope vs. 2. But now each game is equal, with the sequel actually dwarfing WH1 in terms of content, by a wiiiiiide margin, too.
They made all of these plans long ago, and I wouldn't read too much into what GW is doing with Warhammer Fantasy. They're operating on different timetables.