In 5e, Tenser’s Floating Disc
follows you so that it stays within 20’ of you.
The spell description does not make mention of its travel rate, but in 3.5e the description says:
It floats along horizontally within spell range and will accompany you at a rate of no more than your normal speed each round. (3.5e PHB294)
Could the lack of follow speed in 5e be extrapolated from the description in 3.5e?