Here’s a slightly more detailed view of the 12/2016 statistics with the script slightly modifed to filter for Kinetic only.
| Architecture | 12/2016 |
--------------------------
| i386 | 2.33 % |
| amd64 | 23.24 % |
| armhf | 2.35 % |
| arm64 | 1.54 % |
| source | 0.57 % |
--------------------------
|distro_arch | |
--------------------------
| jessie_amd64 | 0.38 % |
| jessie_arm64 | 0.02 % |
| jessie_source| 0.01 % |
| wily_amd64 | 0.27 % |
| wily_i386 | 0.07 % |
| wily_source | 0.01 % |
| xenial_amd64 | 22.60 % |
| xenial_arm64 | 1.52 % |
| xenial_armhf | 2.35 % |
| xenial_i386 | 2.26 % |
| xenial_source| 0.56 % |
--------------------------
Also I found an article on Ubuntu switching to 64 bit downloads by default as of Saucy, on OMG Ubuntu. Clearly there’s some lag.