Elon Musk has recently stated that he wants to send a mission to Mars in 2018 and then send people to Mars in 2024. Those are ambitious timelines for sure, but Musk is nothing if not ambitious.
The real question, the one that matters though, is the nature of the mission. Will Musk recreate the Apollo program, or instead do something smart?
The core problem with space is that NASA has built rockets that go to space, but have built no infrastructure for supporting people to stay in space. This lowers the costs of individual missions, but also means that missions never get cheaper and easier. Without supporting infrastructure, each mission needs to be a self-contained and self-supporting system. Those are expensive.
Musk has said he'll reveal the architecture of his Mars plans in September, so I will reserve judgment on the plans until then. But here's what to look for when that news comes: Do the missions make each future mission easier?
I'll give you can example. Today when NASA sends a probe to Mars, that probe has to bring everything it needs with it. It's own solar panels for power, for instance. If NASA sent astronauts to Mars, they'd have to bring their own air and enough fuel to return back to orbit.
The ideal first few missions to Mars would not bring much science equipment. Instead it will bring tools that synthesize solar panels and wiring from Martian soil. It will bring tools needed to synthesize rocket fuel (liquid methane) from the CO2 and water ice found on Mars. It will bring a big 3D-printer for making pressurized habitats. Etc.
Essentially, the best first missions to Mars will not plant any flags or leave any footprints. Instead they will establish a beachhead. When the first person lands on Mars (possibly as soon as 2024) they should find a settlement and abundant energy and rocket fuel already waiting for them.