Most corporate players will have completed all their FX requirements for the year, as will most of the big asset players as well. Sovereigns were quite busy on Monday doing their year-end square-up and they did the remainder yesterday. In short, most big ‘real’ players will shut up shop for 2 weeks, leaving the market at the mercy of the speculators (which is why I think the big open positions like Yen shorts might be susceptible to some sharp squeezing if no other sellers emerge).
The FX market will remain open but you can expect wider spreads, less liquidity and more slippage. Factor this into your trading equations.