When Lehman Brothers failed, central banks around the world acted to flood financial markets with liquidity. Now the crisis appears to be past and central banks seem to be more inclined to pursue their own national interest. A couple of recent articles at Marketwatch and Bloomberg discuss some of the possible outcomes for the dollar and for other currencies.
Suffice it to say it is complicated. I have no idea if any of their predictions will come to pass, but it is clear that we are entering an unprecedented period where central banks are going to try to stuff the genie back in the bottle. It may well be that a trend-following approach that just waits to see where relative strength appears will be the best way to navigate such complications.
Trend following has worked in the past and will perform into the future for a simple reason: trends exist and they can be traded up and down for profit. You cannot make a profit if you are opposite the trend. While the markets are without clear trends now, the trends will inevitably return.