Ezekiel is one of my favorite books when it comes to end time prophecy. Now I know that there are many different ways that people believe pertaining to Chapters 40-48. Here is my strong belief in the matter. Since the blueprints of the Ez. temple have never been built ever in history or presently, I would be inclined to assume it is pointing to the millenial reign of Messiah, and will be the temple He rules and reigns from. With that said, concerning the feasts, in ch.s 45 & 46 it says as you have said, it mentions 3 of the 7 feasts. But I would be inclined to not think that the other 4 are gone, for in chapter 46, it speaks of the moedim (appointed times/feasts) also the same in the hebrew text. Which would give indication that all still remain. plus, in the Torah, 3 feasts that YAH was adamant about being kept at the temple were, Pesach(passover), Shavuot(pentecost), and Sukkot(Tabernacles).