"About Contest" page says:
- Plugins should be compliant with the IntelliJ IDEA Open API versions 5.x or/and 6.0.
- Winners will be announced on December 11, 2006.
"Terms and Conditions" page says:
- A Plugin submitted for judging ... compatible with versions 5.x and 6.0 of the API
- Prize winners will be notified on or before October 31, 2006 via e-mail or post. A winners list will also be posted ...
I hope the About page is right:
It may be very hard to write a plugin that works on both Idea versions, and may in fact require to completely separate plugins.
Also if end of october is the submission deadline, you should give the plugin some time to prove its usefulness.