Nah, terraforming has never been Elon's immediate plan. He knows that it's difficult and very slow process and won't happen in his lifetime. Their goal is to set up a self-sufficient Mars settlement, which doesn't depend on terraforming at all.

Also, impossible with current technology doesn't mean that it's impossible in the future.

He actually talked about this on his latest Diablo stream, here: https://youtu.be/wzIJDU8SPMM?t=2066 He seems to think that terraforming is possible in the long term, with solar reflectors in the orbit which warm up the planet.