There is only a single upgrade, regardless of subversion. Typically the second release doesn't add too much core technology. The main functionality for the release is available in the first release and the second release builds on this with a few ancillary improvements. As a result, the OCP exam doesn't change much between subversions. There may be some minor modifications, but they rarely change the exam objectives.
You should take the exam as soon as you're ready to do it. Don't wait for the next release.