Here's a trailer for Jon Favreau's Cowboys & Aliens, which is very much about what it sounds like it's about. Daniel Craig is a cowboy who's maybe been abducted by aliens, Harrison Ford is just a regular cowboy.
It sounds like the tone of the movie is actually pretty serious, so don't look for too much "Cowboys AND aliens???" winking going on during the picture. Which, I guess, is fine. I mean, an arch ironic take on the silly premise would almost assuredly be more annoying than a straightforward action adventure about... cowboys and aliens. That's all there really is to say about this.
Cowboys? Yup. Aliens? You got 'em.