Yeah. it sounds like just legendary stuff will be left behind. Exotics should have a way to upgrade, or at least be used in some way to reach Taken King tier. But left behind is a strong way to put it. It's not like they will vanish the day TK drops. Heck, I used my 300 fatebringer through all of TDB (331 cap) and 300 in HoW (365) until I got an etheric light. I can see most of us using VoC, FB, BH, etc for at least a little while.
I wasn't all that excited about TK at first, but now it just sounds awesome. For those that haven't or don't want to read on Reddit, here is a direct cop-y paste summary of what we learned today. So much awesome stuff.
Level cap raised to 40
Cryptarch rewards from engrams are now more in line with the type of Engram you got
The second half of the Taken King apparently starts once you reach the Endgame (Questlines throughout the Destiny Universe!)
Your Ghost can now scan objects to offer more insight into the world's lore (IE, scan a Cabal soldier, gives you info on their Military Regiment)
You can now turn in Bounties without returning to the Bounty Board!
Intelligence, Discipline, and Strength now have numerical "tiers" that decide their influence on your character
A new progress system where you sacrifice an existing piece of gear that belongs to the same slot (? Kind of confused about this and this is literally how it's read)
The Tower and its NPCs have been retooled to offer quests/story/insight into the world as you level up your character from 1-40 (!!!! Cryptarch, Gunsmith, etc questlines!!!!)
Entire base game/expansions retooled for narrative and access purposes to make much more sense (Example: after meeting the Queen for the first time, the Reef is open to you)
Subclasses, old and new, have their own questlines (?)
GUNSMITH NOW HAS A REP AND THE HIGHER YOUR REP, THE MORE "PROTOTYPE WEAPONS" HE OFFERS FOR YOU TO "TEST IN THE FIELD" FOR REP. Reaching a certain Rep with Banshee allows you access to "Armsday", a weekly purchase that allows you to ORDER LEGENDARY GUNS with GLIMMER.
Crucible and Vanguard Marks are gone! ALL HAIL THE UNIVERSAL "LEGENDARY MARKS" FOR LEGENDARY VENDOR PURCHASES!
Class specific materials needed for upgrading are gone! Hadronic Essences, Armor Plating, etc. have been replaced by "Armor Materials", making it easier to utilize materials on one character towards another to progress them.
NO LONGER FORCED TO WEAR A CLASS ITEM WHEN LEVELLING UP NEW MONARCHY, DEAD ORBIT, OR FWC (you pledge to each faction!)
You can turn in materials to these above factions for a Rep Gain (like the Speaker with Glimmer)
NEW SYSTEM THAT RECORDS ALL SHADERS AND, ONCE YOU'VE GAINED IT, YOU'RE ABLE TO CHOOSE FROM THEM ANYTIME YOU VISIT THE SYSTEM (also shows you the Shaders you don't have AND HOW TO OBTAIN THEM!)
Same above system with Emblems!
New Exotics are tied into Questlines!
RAIL GUN FUSION RIFLE HEAVY WEAPON EXOTIC HNNNNNG YE SON YOU READ THAT RIGHT.
Eight new Crucible Maps
Weekly Crucible and Trials bounties! Complete all 5 of the Weeklies for the week, and you gain access to a 6th that has a chance to reward you either a Legendary or Exotic!
ENDGAME THAT EXPLORES PREVIOUS ENDGAME (Vault of Glass) AND FURTHERS TO STORY EVEN AFTER FINISHING THE STORY MISSIONS
Bosses/mechanics that aren't purely Bullet Sponge-y!
Crucible has a "mercy rule"
Game Informer TTK Info Dump Megathread : DestinyTheGame