Originally Posted by Tim_Iowa

Yes, all of Shimano's bar-end shifters for the last couple generations have sold as Dura-Ace. The SL-BS79 Dura Ace 10 speed shifters will index perfectly with your RD-6700.

Your FD-6800 may require more (or maybe less?) lever pull than you've become accustomed to. If you compare the FD-6800 and FD-6700 visually, you'll see that the 6800 has a much taller lever arm. This changes the cable pull required at the shifter. But I don't know if it increased or decreased the amount of cable pull compared to the last generation.

Now the BS79 front/left shifter is friction-only and has tons of lever throw available; it can handle a triple crank. So it should work fine if more cable pull is required. If less is required, then you'll have a very short shift, which would also work fine.