Improving Velocity Estimation Using Multiple Sensors in a Dynamic System
You can do that if you have new data to merge in.
For instance if you have a sensor for Velocity 1 and a sensor for Velocity 2 and in addition a connection between Velocity 1 and Velocity 2 you can use Kalman.

Yet if you have only one sensor for Velocity 1 which with the transfer system you estimate the Velocity 2 there is no additional info to fuse in.

What might be done is that if you have information about the model of Velocity 2 in time you can use that (Though, the right thing to do would be reflect this model into Velocity 1 by the connection of the two, apply Kalman on Velocity 1 and from there infer Velocity 2).