It has been over 6 months since Apple HK sold officially carrier-unlocked iPhone 4 through Apple Store online. Unlike when Apple HK begin to sell iPhone 4 back on July 31, 2010, this time there are no limits on the number a customers can purchase. This is a bit strange since the speculation on why Apple discontinue selling iPhone 4 through their online store and authorized resellers, was because of the overwhelming number of people purchasing and selling them to mainland Chinese gray-market resellers.
With rumors of Apple may be missing the annual iPhone June launch this year, this may explains the reasons why iPhone 4s are back on sale in the Apple Store HK online. The current estimate ship date is "3 - 5 business days", which is 2nd level in the possible estimate ship dates for Apple products sold through the Apple Store online.
This also refutes the speculations that the triple disasters in Japan was going to effect Apple's production lines at Foxconn.