Israel has until the end of the year to bomb Iran, after which it may be too late

Looks like the S-300 missiles will be delivered by the Russians soon.  Once they become operational, it will be much harder for Israel to launch an airstrike.:

Iran will receive the bulk of the S-300 air defence missile systems it ordered from Russia by the end of the year, Tehran's defence minister has said.

"We signed a contract with Russia. It is being done. We will acquire a large portion of the systems by the end of this year," Hossein Dehghan told state television late Tuesday.

He said Iranian troops were being trained in Russia to operate the surface-to-air missile systems.

This week, the state-run Russian Technologies corporation (Rostec) announced the signing of a delivery contract in Tehran for S-300 missiles.