Here's what Gain Capital has to say..
"Summary Outlook: On Wednesday, December 16 at approximately 1415EST/1915GMT, the FOMC is widely expected to announce a steady Fed Funds target of between zero and 0.25%. There has been some speculation in recent days that the Fed may hike the discount rate (the emergency lending rate to banks) from 0.25% to 0.50%, but we think it's too soon for that shift. However, should they move on the discount rate, it would represent a marginal tightening of credit conditions, but should be viewed as another step in the exit process from extraordinary liquidity provision and not as a tightening of monetary policy, i.e. liquidity withdrawal, not a signal on rate hikes. Still, the effect on markets is likely to be risk-negative/USD positive as perceptions of tighter US monetary policy increase. The main area where the Fed may make some changes would be to extend the duration or increase the size of the asset purchase programs, but we also think this is unlikely. But if they did increase the scope of asset purchases, it would likely be taken as a risk-positive/USD negative, as it would be seen to be lending additional support to the housing market. Overall, we expect a very status-quo announcement that will retain the 'rates to remain low for an extended period' language on interest rates and generally note further improvement in the US economic recovery. After past meetings, reaffirming the commitment to low rates for an extended period has been a risk-positive/USD negative, and we expect that to be case tomorrow.
Trading Strategy: We would first note pre-holiday lethargy has already set in to markets, so if we get no surprises tomorrow, there may be only a negligible market reaction. Overall, we are looking for a relatively benign Fed, which should be good for risk sentiment and possibly dent some of the USD's recent strength. In a risk-positive outcome (stocks up/bond yields down) we would expect to see the JPY-crosses move higher, with the USD strengthening against the JPY, but coming under pressure against most others. In a risk-negative result (stocks down/yields up), we would look for the USD to weaken against JPY, but maintain recent strength against most other currencies, likely sending JPY-crosses lower. Lastly, we would note the key support zone in EUR/USD between 1.4450/4500 and the key resistance zone in USD/JPY between 90.20/70 as important levels to watch. "