No, ES6 does not introduce any new number formatting functions, you will have to live with the existing .toExponential(fractionDigits), .toFixed(fractionDigits), .toPrecision(precision), .toString([radix]) and toLocaleString(…) (which has been updated to optionally support the ECMA-402 Standard, though).
Template strings have nothing to do with number formatting, they just desugar to a function call (if tagged) or string concatenation (default).
If those Number methods are not sufficient for you, you will have to roll your own. You can of course write your formatting function as a template string tag if you wish to do so.