Commercial customers are Corporations or other large businesses that can afford to purchase extended support contracts > (Essential and Premier) I doubt the majority of end users can afford this.
From link posted by David Statton http://support.microsoft.com/gp/lifepolicy
Security updates will be available through the end of the Extended Support phase (five years of Mainstream Support plus five years of the Extended Support) at no additional cost for most products. Security updates will be posted on the Microsoft Update Web site during both the Mainstream and the Extended Support phase.
Extended Support End Date for XP Pro is 4-8-2014, after that most XP users will no longer get security updates via windows updates, it is time to abandon XP after this date for security reasons.
Microsoft can change this policy or dates at any time if they wish, which they did for Windows 98 years back due to Corporate outcry, I doubt this will happen for XP but who knows.