Talk of QE3 has been one of the key factors hurting the dollar, but it doesn't mean the dollar's downward spiral is set in stone.

Stephen Jen, founder of hedge fund SLJ Macro Partners and former chief currency strategist for Morgan Stanley, admits, "We are in the scenario whereby the Fed is expected to adopt QE3 despite the acceleration in economic activities," and in that scenario, the dollar should weaken against everything.

However, he warns the biggest risk to that scenario is a "more meaningful slowdown" in China and a not-too-weak US economy. Jen says that combination could potentially trigger a broad-based selloff of risky assets and a dollar rally.