Does app engine have a Deploy Hook or Event?
No.
However, you could get the desired behavior if you write your own deployment script.  This script could be a thin wrapper around appcfg.py which makes a request to your app once the deployment is complete (the request handler can execute the logic you wanted to put in your "deploy hook").
I want to increase the version number on a model whenever there is a new deployment to the server.
So the idea behind this is: Everytime there is a deployment I wanna run some code.
Is this possible within App Engine using hooks or events?
I'm using App Engine for Python.