By Tommy Wilkes and Nell Mackenzie LONDON (Reuters) – The Bank of Japan’s intervention to prop up a freefalling yen has currency investors speculating about which central bank could move next in the face of a soaring dollar. Few think another G7 central bank would be bold enough to intervene directly as Japan did on Thursday. But they say markets should prepare for more verbal intervention and more aggressive rate hikes as policymakers try to thwart the U.S. currency’s ascent. The dollar is up 16% this year against a basket of other major currencies, on track for its biggest annual jump since …