If you want to gain VCP4 and VCP5 you will need to be quick - you will have to pass both exams before the end of February as you said yourself. I would advise to attempt VCP4 before the end of January, and if you pass you still have February to prepare yourself for VCP5. If you don't manage to pass both exams by the end of February you will have to attend vSphere 5: What's New to qualify for VCP5.
If you decide you only want VCP5 and don't attempt VCP4, you will have to attend a vSphere 5 course, I would suggest you would find ICM5 a little underwhelming, it won't challenge you at all, therefore I'd definitely recommend What's New for you.
Scott.
