To repost a previous response of mine:

It isn't crackpot on the order of Ancient Aliens or Gavin Menzies, it just doesn't have much to support it. Pretty much the entire argument rests on a phonetic link of their names, which are exogenous. Against that is a very large gap in time and space, and rather distinct cultures once you get past the "scary horseman" bit (for example, the Huns scarred their chins to stay clean shaven, the Xiongnu wore beards).

It is not impossible, and the archaeology on both ends is too underdeveloped to make definitive statements, but for now the theory must be confined to speculation.

It is worth noting that there has been a real explosion in what might be termed "silk road studies" (which I think of as different from central Eurasian studies, as it examines world history through the lens of central Eurasia) the most recent example being Frankopan's Silk Road. Hopefully this new focus will bring much needed research into this fascinating and often underappreciated region of the world. That being said, the new field has some pretty obvious skin in the game.