I don't expect to hear much about the top four receivers, because they've all been here awhile and the pecking order is pretty well established. Last year Jones vs. Nelson for the #3 spot was kind of interesting, and Jones edged him out, but during the season they played almost the same amount anyway, so it ended up being kind of a moot point.
If there are changes among the top four receivers, they probably won't happen till the regular season gets going. For veteran players, training camp is mostly for polishing their skills rather than competing for playing time.