Information on transferring from old-gen to next-gen ...
I'm pretty sure that you actually keep your progression on the old-gen (360) at the point you transferred. My battlelog BF4-360 profile is showing that I'm level 69 (the level I was at when I transferred my stats), while my BF4-XboxOne profile is showing my current level of 78.
My guess on max levels ...
I have seen a few Colonel 100 emblems. I have NOT seen any Colonels that weren't level 100. I'm thinking that once you reach level 100 then you are finished and have reached Colonel 100. In BF3, you would reach level 60 (or something close to that) and become a Colonel 1 and progress up to 100, so essentially 160+ levels.