The author of this post is doing research on Ben Jonson when she cross-references William Shakespeare and discovers the ratio of material is something like 15:1. She then goes on to do a sort of "tale of the tape" between the two, figuring out how much time one would need to spend reading the material, and basically comes to the conclusion that while one could in theory "catch up" on what's been written about Jonson, this will never be true for Shakespeare - the rate at which new material is appearing is just too fast.
Then she makes the leap that "it must be fairly difficult (impossible?) to write anything new in Shakespeare studies", and that's where I'd disagree. If that were at all true I think people would have stopped, or at least slowed, a long time ago. It's not like we magically ran out of stuff within the last few decades. Second, the world is a changing place. 100 years ago nobody was writing about what Shakespeare might have done with a word processor, or how Henry V compared to George Bush. Lastly, it's not what you write, it's how you write it. If you're saying that nobody can write an introductory book about Hamlet because it's already been written, I'd argue that nobody can write a story about unrequited love because that's been written, too. Sometimes the quality is in the delivery, not the research material.