What is missing is not technology but a reason to go.
"At 1997 prices, a relatively small metallic asteroid with a diameter of 1.6 km (0.99 mi) contains more than 20 trillion US dollars worth of industrial and precious metals." [1]
Spot-checking (pun not intended), those metals are currently up as much as an order of magnitude over their 1997 prices. So that same small-ish asteroid could be worth something more along the lines of a quarter petadollar.
If that's not sufficient reason to strip mine the asteroid belt, I don't know what is.