Bottom line:

On the fiftieth anniversary of Apollo 11, we might see..... Apollo 18.

http://www.upi.com/view.cfm?StoryID=20040728-124356-2684r

NASA's roadmap proposes a first manned landing in 2020, with one landing per year following that.

The see three phases of missions:

-- First, several missions very much like the later Apollo missions, a simple small vehicle (probably using Apollo's single-launch, lunar-rendezvous model), landing in safe, nearside equatorial locations, for stays of a few days to a week.

-- Second, several missions with the same sort of vehicle, also for stays of a week or less, but involving some in-space assembly, and thus able to land anywhere on the moon.

-- Third, more capable missions involving multiple launches, with stays of weeks to as long as three months.

Note that puts the long-duration missions not happening until nearly 2030. I'll let you make your own guesses about what sort of timeline that would put us on for a Mars landing.