Of course, there is no chance that the congressional district system will be adopted for the entire country between now and 2016. There is no interest in changing the method of awarding electoral votes in states currently controlled by Democrats or in states currently controlled by Republicans that were carried by Romney in 2012. Adopting the congressional district system in those Republican states would probably help the Democratic presidential candidate in 2016. But there is a chance that this system could be adopted by six battleground states that were carried by Obama in both 2008 and 2012 but where Republicans currently control the governorship and both houses of the legislature: Florida, Michigan, Ohio, Pennsylvania, Virginia and Wisconsin.
If these six battleground states were to adopt the congressional district method of awarding electoral votes, it would not guarantee a Republican victory in the 2016 presidential election but it would make such a victory much more likely. That's because the congressional district lines in these states were gerrymandered by Republican legislatures following the 2010 census to give their party a huge advantage. As a result, even though Obama carried all six states in 2012, it appears that Romney carried 61 House districts in these states to only 33 for Obama. Romney appears to have carried 16 of 27 House districts in Florida, 9 of 14 House districts in Michigan, 12 of 16 House districts in Ohio, 12 of 18 House districts in Pennsylvania, 7 of 11 House districts in Virginia and 5 of 8 House districts in Wisconsin.
If the congressional district system had been used in these six states in 2012, instead of Obama winning all of their 106 electoral votes, it appears that Romney would have won 61 electoral votes to only 45 for Obama. As a result, Obama's margin in the national electoral vote would have been reduced from 332-206 to only 271-267.