Ezekiel's Temple is Past

Ezekiel 43 says the instructions about the Temple, which Ezekiel was to write for Israel, were for Israel to carry out.

How could they carry it out if it's still to come in our future?

Therefore his vision of the Temple was not about some still-future Temple, but was about that Temple with which the Jews were concerned during that time of captivity. 

Admittedly some descriptions of the Temple were too grandiose to have been carried out literally at that time - but that's explainable by the fact that not all Ezekiel's writings about the Temple were intended as literally instructive - some were simply descriptions of visions, and were written not in prose but in the apocalyptic genre.