WISE will see many galactic stars in the short wavelength channels, and many luminous IR galaxies in the long wavelength channels. Simulations of the North Galactic Pole are shown below, in the three long wavelength channels (4.7, 12 and 23 microns):
This image covers 2048" with 4" pixels. Click on it to get a larger version with the full WISE resolution.
The many blue dots in the above figure are mainly galactic stars and normal galaxies. The red dots are galaxies with redshifts close to 2. I have included a 200 K brown dwarf at the distance of alpha Centauri just below the center in this figure, and the ULIRG F15307+3252 shifted to z=3 just above the center. An asteroid trail crosses the center of the picture as a string of yellow dots. WISE should see 1 or more asteroids of this brightness in every field this size.