Reading like it was 1813

Footnotes may be boring to actually read, but they are interesting as a concept. That said, if you were thinking of getting me this new hyper-annotated version of Pride and Prejudice for St. Patrick’s Day, please just give me the cash.
According to the NYT,

Any reader who sticks with the program and absorbs the wealth of material that Mr. Shapard offers will, insofar as such a thing as possible, read “Pride and Prejudice” as it was read and understood at the time of its publication, with all the period details in place and correctly interpreted.

I'm glad I can finally read P&P as if I were a real person in 1813, stopping every three seconds to read a footnote just like they did!!
Here's a question: how much do writers consciously write for posterity? It seems like most of the "contemporary fiction" I own will have to be footnoted like crazy for audiences a hundred years from now. As opposed to the MC, which is timelessness if I've ever seen it (AND I HAVE).