There will always be value in short domain names.
There are only 17,576 possible LLL combinations. Add a letter and that's 456,976 LLLL combinations. One more and that's 11,881,376 for LLLLL domains.
That said, with 500,000 words in the English language (according to Oxford dictionary), along with every possible prefix and suffix add and intentional misspelling (i.e. Flickr), there are virtually endless two word combinations.
Sure, certain combinations (i.e. UsedCars, InsuranceQuote, FreeStuff, etc.) are worth more than the majority of LL or LLL .com's any day of the week... but the rarity factor still plays a role in how valuable shorter domains are.
With thousands of domains being registered every day, the number of active domain names will simply not go down, making the LL and LLL's even rarer.
As I said with an LLL .ca name recently... if the letters don't abbreviate something, it's an investment name. I'm not the only guy here who knows this, which is exactly why LL and LLL .com's get multiple offers, and a "wholesale value" has limited meaning.