hehe Lots have happened 
Too much to really detail every change, but overall, new powersets are Dual Blades, Willpower, Pain Domination and Shield Defense. There's also "old" powersets on new archtypes. Like Scrappers now have Fire melee and Fire armor. Brutes have Axes, Maces and Super reflexes. Controllers have Plant domination etc etc.
IO's or Invention Origin Enhancements are a "new" type of enhancement. Crafted with a recepie, salvage and inf. They have an advantage they don't gain/lose effectiveness at you level up. They always give the same bonus. There's generic IO's which boost one attribute, much like SOs. But the higher level the IO the better the bonus.
Then we have something called "set IO's" which when slotting IOs of the same set they will provide additional bonuses. Diffrent powers take diffrent sets. These IOs will also often boost 2 or more attributes, like dmg/end. or end/rchg/res, as an example.
This opening up many new ways to slot your powers and make you utterly ruined inf wise
Thats just a basic overview, i recommend visiting a university and take the Invention tutorial and read it, it mentions pretty much what you need to know.
You can use the Black Market(villains)/Wentworths(heroes) to buy and sell your recepies/salvge/enhancements/etc
Be advised that the villain (Cap au Diable university, started by Dean John Yu) invention tutorial has 88% more "funny" than its heroic counterpart. Reading all contact bios strongly recommended. 
Regarding new content, the relatively recent big pieces are:
Ouroboros - gives access to outleveled story arcs and badge missions.
Cimerora - ancient roman zone, both villains and heroes, must do a story arc to enter it. Has a few story arcs, repeatable missions and a level 35-50 co-op task force.
I do not suffer from altitis, I enjoy every character of it.
Left around when Villains got their Issue with Grandville&patrons powers.
What happened since then? New Story arcs, New Zones, New powersets? Talking about powerset, any "buff" or "nerf"?
IO's, what are those? I see these everywhere in Archetype builder, I understand those are inventions, you can "craft" them? If so where at?
If you guys have a link or good enough to write the list, I'll be very grateful.
PS : Yes Max, I'll up my sub once again.