Wait and see what content is in the main game.
Like love EU4, that game has had like 10 expansions+ over the past 4 years. I have spent probably over 150-200 on that game. But the reason it is not an issue? The base game had a ton of content, the expansions added new mechanics many of which are essential due to some changes made in free patch others because they enhanced the game so much playing without becomes unthinkable.
It is a simple test. If a game at launch has enough content that if nothing else ever released it would be fine then I have no issue with it. If the game is clearly a shell then we have an issue.
Destiny 1 was tricky. There was 100s of hours in the vanilla release if you enjoyed it, but at the same time it clearly was a bit short on multiplayer maps and co-op strike missions. 1 raid was fine due to the way it was structured that it would takes weeks for most groups to conquer it the 1st time.
IMO if Destiny 2 is more balanced out of the gate than Destiny, and has maybe 2-3 more multiplayer maps and 2-3 more strikes I have no issue. I am all for massive content drops on top of that.
End of 2009 Predictions (Set, January 1st 2009)
Wii- 72 million 3rd Year Peak, better slate of releases
360- 37 million Should trend down slightly after 3rd year peak
PS3- 29 million Sales should pick up next year, 3rd year peak and price cut
