This is the proposal: https://notes.ethereum.org/SCIg8AH5SA-O4C1G1LYZHQ?view
Summary of the deprecation: https://medium.com/@djrtwo/casper-️-sharding-28a90077f121
Said in the most light-hearted way that I can manage: I am reading this article about merging two complex initiatives as I reach for my paper copy of “The Mythical Man-Month”.
Definitely need a concrete plan for testing each one of these ideas either atomically or after successfully proving any prerequisites. This is a much more complex proposal from Casper FFG, and requires more solid planning.
For example, the random beacon chain could be something useful for a variety of games that require a source of randomness. Many different low stake use cases can show robustness before the entire network moves to the new design.