Knold,
The size of the vortex is directly related to wingspan. Terminal velocity, which is the highest velocity the air can achieve, is constant through all aircraft types. The size of this core is not. Looking at the A380 in the video, you get an idea of the size of the vortex on rollup, note that it is about exactly the length of the individual wing.
What you do see remaining is the high velocity core of the vortex.
Note that the wake core is not really descending in this video. (nor drifting sideways)
look at this beast of a wake...