Predicting the landing site of a saccade while the saccade is still in progress
Interesting question! Trying to interpret your question, I think what you are after is a model that can predict the saccade endpoint based on eye tracking data? 

The following answer is more of a basic neuroscientific approach:

The neuronal responses (spike rates) in the superior colliculus (SC) can be accurately used to predict the total saccade as a vector. Basically, when you model the response properties of all the SC neurons involved in a saccade, one can calculate the vector sum of all these different neurons. With this vector sum the saccade can be totally described in terms of its direction and amplitude. With the vector sum, hence, the end point can be predicted. 

If this subject is of interest to you, the early work of Van Gisbergen and John van Opstal (based in Nijmegen, the Netherlands) are a good source.

Reference:
Van Gisbergen et al., 1987