Source: http://www.swtor.com/community/showthread.php?p=7821913#edit7821913

Here goes everyone. Here is the information on the conversion rates around Basic Comms and what will happen when 3.0 launches. Just to reiterate for those unaware, here are the basic changes coming to Commendations:

• All PvE Commendations will become Basic Commendations in 3.0.
• The Commendation types "Classic" and "Planetary" are being removed from the game.
• The types "Elite" and "Ultimate" will remain but the current Comms you have will become Basic.
• Warzone and Ranked Warzone Commendations remain untouched.

Here are the conversion rates for all Commendations.

• 2 Classic Commendations = 1 Basic Commendation
• 1 Basic Commendation = 1 Basic Commendation
• 1 Elite Commendation = 2 Basic Commendations
• 1 Planetary Commendation = 3 Basic Commendations
• 1 Ultimate Commendation = 3 Basic Commendations

The Basic Commendation cap will remain at 1000. However, when the conversions happen we will allow you to go up to 2000 Commendations. Note that until you go below 1000 again, you will be unable to earn any Basic Commendations. This includes if you buy an item and try to refund it. You must go below 1000 before you can earn more.

There ya go folks! All of the details and conversion rates on Basic Comms in 3.0.