Depends on how much room I have. Both are seriously sharp lenses, but if I will be shooting in cramped quarters, the 50mm is good; if I have a bit more room, the 85 comes out so I can really get great background bokeh.
I think what you have should be good enough. 85mm may be a bit too long on 1.5x crop. 135mm would not give you a useful working distance. Unless your 16-80 can already do so, an alternative would be to get a Macro lens in the range of 55 - 105mm for objects like rings, flowers, tea cups, etc..
Yupp, like others have said, 85mm would be good for weddings I guess.
Since a wedding is a rather fast paced event, have you considered a zoom? They might not be as fast wide-open or give the best IQ (comparatively speaking), but they allow for a quick switch between focal lengths.
Since you use a crop body with 10-20 + 50mm, I think a good option is to go for the 70-200vr. If that's too expensive, and you don't really need the reach, I think that either of the 2 poll lenses will suit you. But since you have 80mm covered already, would a faster 85mm be of much importance to you (It might be, but I don't know what widest-aperture your zoom allows at 80mm).
I already have a zoom. A 16-80 f/3.5-4.5. Versatile and sharp, but just a bit harder to achieve depth of field effects. I've demo'ed the 85mm, and somehow, it just makes the subject pop out of the frame.
I'll probably settle for the 85mm. Now I've gotta sort out another problem - raising the funds for it!