I will point that the article in the OP and the article it cites are both from the WorldNetDaily, a crazy conspiracy hub pretending to be a conservative news site.
The IIF press release, as well as the actual policy letter that they mention, says absolutely nothing about a single global currency. The point of the policy letter was to encourage the G20 to agree to a mutually beneficial framework for future moves in the international currency market to avoid currency destabilization in the current global economic environment.
In other words, convincing the US, EU, and China not to short one another's currency as a fiscal policy.
Not a thing about one world currency. Which would make sense, since banks make such a ridiculous boatload of cash by acting as clearance houses for currency traders.