Neji had to die because he and Hinata made each other redundant in the K11. What with having the same jutsu, they were competing with each other for panel time. Since Hinata was the less advanced Jyuuken user of the two, she hardly ever got to show a new jutsu - she was pretty much always unveiling last year's Neji jutsu, or a half-assed version of Neji's jutsu. With Neji gone, Hinata can showcase all of the new Hyuuga jutsu as Kishi thinks them up. What's more, she can go on more missions, get more panel time, and NaruHina can finally become a reality (although NaruSasu seems more likely).