For your purposes and needs, I would say either get the 5d2 or 6D. Think of it this way. If you get a 5D2 or 6D, you an use the money you saved towards some nice glass. You said you have the EF-S 15-85, EF 50/1.4, and Tamron 70-300 VC USD.
You're no longer going to be able to use that 15-85, so you may need a standard zoom and maybe an L lens or two. You can used that saved glass to get the new 24-70 f/4L IS, which has that special macro mode on the tele end. That is a good solution to your standard zoom/macro needs. The 50 can be used for your portraits.
The 5d3 does have more AF points, but you only really need those for sports or BIF. Although I got the 5D3 before the 6D was announced, I still wouldn't change my decision.
I shoot a lot of sports/action so I need the 61-AF system and the 6fps. However, for portraits/landscapes you don't really need those extra points or the extra burst. I used the 60D and was frustrated by its tracking capabilities.
Build-wise, the 6D is by no means a pushover. It has a magensium body with a polycarb top. Coming from a 60D, it would be an upgrade for you either way.
Image-wise, the 6D is not going to be a slouch either. It may even be possible that the 6D has slightly better noise performance because it has less pixels crammed into it. Personally, I'm really interested in how the extra-sensitive center AF point performs. If it performs as its touted to be, that will be huge for lowlight shots.