As of 7.2 revision management supports creation of multiple parallel revisions by having multiple overlays. But there will be only one open revision per overlay. So the answer is NO, we can't create multiple revisions in one overlay.
If there will not be any common rule between the two revisions then you can create multiple overlays to address two business change requests in parallel.
In 7.2.2 we are going to enhance the revision management to remove the restriction on adding same rule to different overlays. So that users can create multiple revisions for same rule and deploy them.