This has been in the works for years. Never took off.
At one point, Brittany Spears and Justin Timerblake were children to "Danny" and "Sandy" - and the film would have tons of cameo appearances with pop stars and Grease alumni from the previous 2 films.
"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