Quote from JackR:
It is difficult to believe that the IRS, the brokers, and the tax program people will not have things pretty well figured out by the start of the next tax season.
I trade futures so I don't pay much attention to mark-to-market. But if there are tax advantages to you not being mark-to-market it might be worthwhile waiting. As I understand it, once you've made the declaration you are stuck with it for that year and must undeclare, if desired, for future years. Otherwise, it persists without further action.
Jack