Hi Adam ,
The only issue can be that you will not be learning about all the new features of Excel 2013 , which is as much of an advance over Excel 2007 , as Excel 2007 is over Excel 97 !
Also , though the class may use Excel 2007 most of the time , there may be coverage of the additional features in Excel 2010 , such as Slicers.
Learning about Excel 2007 together with Power Pivot can help , since the latter is an integral feature of Excel 2013.
Of course , whether you will need to use all of Excel 2013's features in the course of your day-to-day work is for you to decide ; I feel that if you are a novice at Excel , the class will be beneficial ; what ever mastery you attain , you can take it from there , and learn about the other features in Excel 2013 on your own.
Narayan