Catherine Eagleton is the Curator of Modern Money at the British Museum.
She asked to send her examples of anything that should be preserved.
"she also mentioned in passing how difficult it is to think of ways to preserve World of Warcraft gold pieces or Facebook credits for posterity http://digitaldebateblogs.typepad.com/digital_money/2011/03/still-going-strong-after-14-years.html
I'm thinking that a wallet.dat containing the generated bitcoins from a very old block, even if the bitcoins have since been spent, would be a candidate for preservation.
That's all long before I knew of Bitcoin, however.
Her contact info: http://www.britishmuseum.org/the_museum/departments/staff/coins_and_medals/catherine_eagleton.aspx
As an aside,
I occasionally see numismatic value of bitcoins discussed.
There are thousands and thousands of early blocks whose generated 50 BTC have not been spent yet. These will be interesting, because there's no way to tell if the wallet has been copied previously. Its value will come from knowing how secure it was previously, especially if it has changed hands.
Are virgin bitcoins (generated but never spent) the equivalent of the "uncirculated" grade assessed a physical coin?