You must have seen the report where this comes from, but like most people and unlike that guy (he thinks the real Lanfear is also in Finnland waiting for Mat to rescue her...) you understood it as a joke at the time. It was pretty obvious from the way the reporter conveyed the tone of Brandon when he spoke of that
Someone was assuming a little too much to Brandon's taste in his questions that Moiraine would be rescued and Brandon went and answered something like "what makes you so sure Moiraine will be rescued in the next book, or will be rescued at all?".

If you remember, Brandon was the one who blundered long ago and revealed that Moiraine is alive, because he thought there was a confirmation of that in KOD.

There's very little chance Moiraine is rescued only in the last book. Mat's not going to spend all of TOM making dragons with Aludra, Thom is pressing him silently already and we know Mat has to be back for the "reunion", so he won't go to Ghenjei in TOM but not return until AMOL....

My personal bet is that Moiraine's rescue happens in the second half of TOM. My theory is that it will held Mat away from the beginning of the big battle that starts TG (which I'm convinced will happen at and around Caemlyn). He return in the middle of it to begin to turn the tide.