In a word, nothing.
Traders expect the Fed to acknowledge that the US and global economies have both shown recent improvement but that it is too early to sound the all-clear. They very likely will maintain their stance that rates will stay low for a considerable period.
The wildcard will be how the Fed will deal with the impending end of the program to purchase $300 bln worth of Treasuries by mid-September.
We’d like to see them end the program, which would be a boon for the dollar. More likely, they will keep all options on the table with some vague statement that the program is being reviewed. An explicit extention of the program, like undertaken last week by the BOE, will be bad news for the greenback.