Here are a couple of spoilers that I was able to catch:
1. No, Naraku does not die! LOL
2. InuYasha's sword becomes yet stronger (After Kongo~suha, there's also Dragon scale, Mido~ Zangetsu~ha).
Kikyo~ merges with Midoriko (The main person which the Shikon Jewl emereged from). After a number of chapters, she dies!
(Don't really remember how)
Miroku (I'm not so sure), but I heard that he dies as well (don't think so though).
3. Kagura dies in the first season. Hakudoshi dies as well, Miroku's sucks him with his Kaazana.
4. Kohaku (Sango's lil brother) dies as well, Naraku eventually takes the shard from him.
5. Kouga (the wolf) gains a new strong weapon (super claws, its like a glove).
First, his sword "Tenseiga" becomes a weapon instead of a healing sword (for a change of heart). Shortly after
that, he challenges Tetsusaiga (InuYasha) and Tetsusaiga's new technique (Dragon Scale, which sucks the enemy's youki
power) sucked all of Tenseiga's super power "Medo~ Zangetsuha", so the technique becomes originally for
Tetsusaiga (This is what their father wanted Sesshoumaru to master, so InuYasha can take the technique for Tetsusaiga
While Sesshoumaru is in battle with a really strong enemy, the enemy pierces him through his body (Big hole), at the
moment he totally "GIVES UP" on Tetsusaiga, and grabs his Tenseiga. The moment he grabs Tenseiga, the hole in
his body vanishes (heals), and his left arm returns in a flash! Sesshoumaru becomes "almost" invinsible, and
his "REAL" sword emerges: "Bakussaiga"...
Well, that's all I can remember, I hope its a good spoiler! LOOOOOOOOOOL!