I don't usually make posts (since I don't know any Korean), but I've tried my best to gather some links, images, and videos that briefly explain the coming.
Video by ReCounter Vindictus explaining the content:
Laying out its contents here too:
1. There's a new raid: Ragnahim
More info (but in Korean)
http://heroes.nexon.com/News/devnote/View?postno=357
B TANK's spear Lann solo:

Cutscene:
2. Tower of Bewilderment
(A solo tower climbing instance)
more accurate info (in Korean)
http://heroes.nexon.com/News/devnote/View?postno=356
Edit: Explanation video by ReCounter Vindictus

Gameplay by MintRisha
3. Friendship skills
These were already shown in a previous post, here they are again.
Released combo's so far: Eira & Arisha | Lann & Lynn | Karok & Delia | Evie & Lethor | Miri & Hurk
Predicted future combinations based on special interactions: Kai & Vella | Sylas & Bel

Cleaner version for Karok and Delia
4. Lens items

There's also changes to the cosmetic system, but I don't know exactly what.
5. New character
The team has said they are working on a male character. We can expect to see him in July. According to the translation by ReCounter Vindictus, this will be his weapon:

(Personally, I would have liked to see a more interesting type of weapon, possibly even magical, but we'll see how he plays.)
Some other videos:

---
"In August,the whole new content update will be made that has never been done in Vindictus ever before."
---
That was a long post!