We can be sure only after we see the games for ourselves, but yeah- in all probability the games on the Xbox One will look better than with a 7850. Maybe not during the console release, but surely after an year. The GPU in the Xbone is (rumored) to be the equivalent 7790, which is slightly worse than a 7850. But remember that it's always easier to code for a console, so in a year the devs will learn to juice out more power from the Xbone.
I really don't know much about hardware either, but despite the new console having the x86 architecture, there are still a lot of differences between the hardware of theses consoles and PC- so we can't tell a lot by only comparing the GPU; only time will tell for sure. But as I said before, the Xbone wil most likely outclass the 7850 and even the 7870 within an year.