I really don't know, everything is possible. Perhaps they don't want to go through the hassle of updating the developer preview, but then it would also make sense for them to update it to continuously check if the changes cause any problems on a large scale.
i honestly don't understand what kind of response these questions expect to get, everyone is basically in the same boat with regards to what google's plan is regarding anything with L
There will be updates. What Google has on their website is, "Updates to the L Developer Preview are delivered in the Android SDK Manager. Check back periodically for news about the changes." It almost sounds as if updates will need to be flashed but they aren't really clear.