1) In 2012, the exams for version 7 were introduced.
2) Because Oracle decided to split it up (and add more material to the OCP). You can still take the OCJP 6. In fact you can still take the OCJP 5. Oracle is slow to remove exams. I wouldn't recommend taking verison 5 though as version 6 is so similar.
3) I wouldn't recommend it. There's a lot of new material on the OCPJP.
4) Plus the K&B version 7 book is coming out this month. You might as well wait at this point if you want to take version 7 of the exam.
5) The beta of the OCA 8 is already available. I wouldn't use the
word "suddenly" though. Oracle doesn't move quickly in this space. Version 6 and 7 of the exam aren't going anywhere so pick one of those and take it. Oracle has to get rid of version 5 of the exam before getting rid of any others.