Apple's MacBook Pro (which was announced in January 2006) is currently referred to by Apple as "Early 2006".  This simple naming scheme would indicate that a revision at some point in 2006 is very likely.  An example that demonstrates the naming convention is the Apple document that refers to the April 2006 firmware update for the MacBook Pro.   Note the reference to "early 2006" at the top.  Apple's most recent update to the iMac is referred to by Apple as "Late 2006" whereas the prior models are referred to as "Early 2006".

Note that in 2005, Apple released two versions of the iMac, Mac mini, and PowerMac G5.  Apple's documents of interest:

• Mac OS: Versions, builds included with PowerPC Macs (since 1998)
• Mac Specifications
  

The early 2005 models were referred to by Apple as "Ambient Light Sensor" and/or "Second Generation.  Then Apple started to use the "iSight" classification for the iMac released in October 2005, it's also referred to as the "Third Generation".

• Early 2005 (Ambient Light Sensor and Second Generation)
  
• Late 2005 (iSight and Third Generation)
  

The Mac mini was first relesaed in Janaury 2005.  The revision in September is referred to by Apple as "Late 2005".

• Scroll down to Mac mini to view
  

Apple released two versions of the PowerMac G5 in 2005 the April release is classified as "Early 2005", the October release is classified as "Late 2005"

• Early 2005
  
• Late 2005
  

• Added evidence of Apple product revisions and naming for 2005