How much AWS could they really get? Buying up Metro and Leap would probably cost them somewhere around 15+ billion dollars, and that would only give them around 10Mhz of nationwide AWS. I doubt they would ever get a good enough amount of AWS.
Sprint has almost complete nationwide coverage using just Block A and B, which are 30Mhz blocks, plus more in blocks C-F, which are 10mhz and 10Mhz nationwide on the G-block
If you do not trust that source, One of our contributors, AJ, created this map some time ago of Sprint's spectrum holdings.
Even if we go by this map, Most areas are covered in 30Mhz of spectrum. This map does not include sprint's G-Block either.
Unless Sprint decides to buy the spectrumCo AWS, they will not get enough AWS for it to matter. It would be better to focus on bolstering PCS holdings, Buying Clearwire( which including debt would be cheaper than Leap or Metro), and possibly buying the rest of the SMR in the future.