IPUMS-USA is currently evaluating different methods for generating these RACESING variables from multi-year ACS samples. Unfortunately I do not have more information regarding the expected release of these variables at this time. However, since the multi-year ACS samples are actually just an aggregation of single-year samples, all of which contain the RACESING variable, you could combine the single-year files to create a multi-year file from 2013 or 2014 with RACESING.
I hope this helps.