GREASE 3 is old news. Scripts have been written for a few years now. Originally, John Travolta and Oliva Newton-John were planning on doing a sequel, with pop stars as their kids, such as Britny Spears and Justin Timberlake.
However, there was script problems, among other issues.
Now Travolta doesn't want to do it at all (good for him) and another version of the script has been re-worked. At the moment, doesn't look like it will happen. But who knows?
"The Spectacle has, indeed, an emotional attraction of its own, but, of all the parts, it is the least artistic, and connected least with the art of poetry. For the power of Tragedy, we may be sure, is felt even apart from representation and actors. Besides, the production of spectacular effects depends more on the art of the stage machinist than on that of the poet."
--Aristotle