Sahil,
Web based plotting is something that many people desire and are working on at the moment. One or more of the existing projects (or a new one) are going to be the next generation plotting that everyone uses. SymPy, on the other hand, doesn't really need to compete in this plotting race, we simply need to use whatever the best plotting libs are. In the long term, SymPy's "plotting" functionality should simply output data that can be consumed by the most popular plotting libraries. SymPy Gamma will of course need to output to the most popular web plotting library. Most of the core devs seemed to agree with this when we reviewed the GSoC proposals. But, also which proposals we choose are based on a lot of factors: proposal quality, patch # and quality, interaction with the community, available mentors, project fit, likelihood of success, likelihood of use, etc. For a combination of those reasons, your proposal didn't make the cut. Maybe others can comment more on specific feedback about what you could have done to improve your chances of success with GSoC.
Thanks for your continued interest. We can still help you move forward with your ideas.