I checked the study guide at
and do not find my of the ecosystem projects like Avro, Parquet, Flume, Sqoop, Pig, Crunch, Spark, HBase and Zookeeper.
Can I expect any of these on exam?
The only mention I see is of Hive and Oozie.
Also how frequently the exam changes? I planning to take this in January. Can I register now and schedule for that time?
If something is explicitely mentioned, you'll want to know at least what it tells you to know about it. Sqoop is mentioned btw. For the others, I'd want to have a good grasp on what they are and how they can be utilized; if not for the exam, just for practical purposes of being able to work well in Hadoop.
I can't speak to how often the exam changes and what that would mean for your studying by purchasing early. You can certainly purchase early but I'd weight the unknowns of doing so versus the value-add of registering early before making a decision.
hope this helps in some way.