Given that Destiny 2 will most likely function identically to TTK (i.e. an enormous expansion) I don't think you could really say it will 'kill' Destiny. That's beyond the point anyway, the thread is clearly referring to the franchise including dlcs/sequels (much like WoW is taken to mean the full game in its current state with all expansions/content - not the vanilla game that was called WoW with no subtitle).

Doubt it will only be TTK size. It's a whole new game not an expansion.

Oh no you misunderstand - I agree that it will be far larger than TTK, but it will still function as an expansion. It will run off the same engine, you'll have all the exact same year one content on your director, you'll bring everything you have across etc - it will just be a whole bunch of new director locations essentially, with new additional weapons and armour, new LL cap, and some minor changes to existing locations (e.g. taken removed, replaced with some new world events)

Exactly!! If what you say is true and all that is coming forward, then there will be minimal reason to still play destiny one you know?