Whatever race they have, they wont be able to have the name "olympics" in the title or marketing, or even have any olympic rings logos in any PR or finishing pictures due to the way the IOC do the copyright. So my guess would be the local council will be the ones to put something on under the new name (Queen Elizabeth Park or something I think).
Slightly related, there are loads of races if you fancy running round dorney lake (where the rowing and sprint kayak was). One lap is basically 5k, so they have several 5k and 10k events, plus duathlons there thoughout the year. Although its an open site, so providing there isnt a regatta or...or the olympics....you can just show up and go for a run anytime.
F3 events do all the winter ones and 2013 dates already locked in. Wont be the same as the olympic park, but its as flat as flat can be if you fancy a PB.....unless you get unlucky and its a really windy day. http://www.f3events.co.uk/ Hoping the leave the big olympic rings up at the site, but for the same copyright reasons, pretty sure they'll be going.