The way I see it, Destiny on disc is deader than the dinosaurs as soon as they stop support and flip the switch on the servers. It's very much a game as a service, so digital is the best way to go since you won't be able to play this in 10-15-20 years without Activision re-releasing it.
MP only and games as a service games are where I go right to digital, besides super cheap sales for a license.
Yep, Destiny feels more like a game client than anything else on console considering the amount of updates, iterations, and expansions hence why I originally would not have been shocked to not see a number in a major follow-up's title as I simply don't think it's needed especially with the Year 1, 2, 3 classification. This is in a different context though compared to saying the the number "2" is dumb or whatever as I couldn't care less what they call it I'm just happy a major release is around the corner as more Destiny is always a good thing.
That said, one final thing on the naming...it isn't like I referred to Destiny every time I spoke of it as whatever version we were currently playing like "Destiny: The Dark Below" or "Destiny: The Taken King" but rather simply spoke of it as the all-encompassing "Destiny" which I imagine a lot of us will continue to do. The only time the sub-titles would even come up would be when speaking of when they added/changed things, etc.