Wind tower bases are designed principally for stability, not just as a slab of concrete to bolt a tower to. To achieve that stability the base must be able to resist overturning due to ...
The base must distribute these forces on to the ground without exceeding the bearing pressure for that particular soil.
Therefore it is ridiculous to say that a wind tower in 50 years time will exert the same forces on the base structure as the one that structure was designed for.