You might not have noticed but this month (last January 10th) ISA Server 2006 Mainstream Support ended as shown in the table below:
The question that you might have is: what about this extended support that goes until January 2017? Extended support means the following:
The Extended Support phase follows Mainstream Support for Business and Developer products. At the supported service pack level, Extended Support includes:
Better to start planning your migration as part of your new year’s resolution.