Traditionally there is a set time when no class is required to upgrade to the new cert. After that time you need the 2-day "what's new" class - as long as you are only 1 version behind.
If you are VCP4, you needed just the exam for the first x months (I forget how many, 3? 4? 6?)
Now, you need to take the "What's new in v5" plus the exam
If you are VCP3 you need to take one of the 5-day classes, or switch to VCP-Cloud which has a 3-day class.