The fed are looking at two main indicators, unemployment rate and inflation.
"In determining whether it will be appropriate to raise the target range at its next meeting, the Committee will assess progress--both realized and expected--toward its objectives of maximum employment and 2 percent inflation. " (source)
The maximum employment occur when unemployment rate reach between 5.0%-5.2% (source),
which had been reached according to latest unemployment statistic from US bureau of labor statistics (here)
However, core inflation remain low at zero level (source), i believe mostly thanks to collapse in crude oil price and appreciation of dollar. As crude oil price is expected to remain low in foreseeable future (see here), and there is unlikely for dollar to depreciate soon, given all major economies around the world (EU, China, Japan) are still trying to pump liquidity to revive their economy growth pace, the core inflation rate will likely remain low in foreseeable future.
Even if the inflation rate do climb beyond 2%, the Fed will still likely wait until the trend (inflation) become firm before taking further action, as per below statement:
"The Committee currently anticipates that, even after employment and inflation are near mandate-consistent levels, economic conditions may, for some time, warrant keeping the target federal funds rate below levels the Committee views as normal in the longer run."- source
The implication could be that, the longer the Fed hold off in raising rate, the less attractive it is to hold dollar asset, and the more undervalued emerging market asset could reach.
