Yes. Unfortunately he does die in episode 24. I do not know if he comes back to life. There are rumors that he does come back in the movie, but I have no idea. Sorry for the sad news.
Lots of people are saying he's going to come back in the fifth season. (yes, rainbow is working on 5th season). They are saying he did not die and is just in a coma. Hopefully they are right. (Seriosly, winx being a kids show, wouldn't it have a happy-no death policy. seriously! i sure hope he will come back