I don't think there are any short term plans to certify Alfresco on OpenJDK.
Edit - and looking back through these forums it looks like the problem may be with OpenJDK rather than Alfresco.
If you are an enterprise member and need this then please speak to alfresco support who may add OpenJDK to the list of supported platforms.
If you are a community member and need OpenJDK then a first step is to enter a good description of the problem in issues.alfresco.com. Then others can vote for it and contribute fixes.