“We were focused on 2018, but we felt like we needed to put more resources and focus more heavily on our crew program and our Falcon Heavy program,” Shotwell said at a pre-launch press conference in Cape Canaveral, Florida. “So we’re looking more for the 2020 timeframe for that.”While not specifically mentioned, this puts the launch of Red Dragon in the June to August 2020 timeframe. The orbits of Mars and Earth line up favorable about every 26 months so that is the ideal launch window for a 2020 mission to Mars.
If the mission succeeds, Red Dragon will by far be the heaviest object to ever land on Mars. Red Dragon weighs 6400kg and supports a payload of up to 2000kg, compared to a weight of just 900kg for the Curiosity rover. In fact, Red Dragon's mass is higher than the sum of every other object which attempted to land on Mars.
In related news, SpaceX will be launching the CRS-10 mission later today. Less than 4.5 hours from now this rocket will be on its way to resupply the International Space Station (ISS). A livefeed of the launch and a countdown clock can be found at SpaceX.