According to AP, The IOC will be retesting select samples from the 2008 Olympic Games in Beijing. Drug testing technology improves every year and the statute of limitations on testing was recently increased from 8 to 10 years, allowing anti-doping agencies to go back and retest older samples. 

Keeping in line with new testing protocols, the goal of the test isn't to cast a wide net and retest every possible sample but instead to retest athletes who competed in Beijing who may compete in Rio. Much like the testing that occured at the IWF World Championships last November, this is a focused and surgical task deliberately aimed at making sure athletes who may have doped in the past do not get to compete again.

Alexey Lovchev, who was caught for doping after breaking several World Records at 2015 IWF World Championships, will not be competing at Rio. The methodology involved in testing for the drug he was taking was only recently developed, and it'd developments like that which will be put into use when retesting old samples.