In an interview between Ian Cameron Esslemont and Elitist Book Reviews, the final two Malazan novels in his series have been named.
We knew that the Darujhistan novel, Orb, Sceptre, Throne was up next (out in December in the UK), but he has confirmed that the next book has the working title City in the Jungle, will be set on the continent of Jacuruku and will feature the Ascendant Ardata. The sixth book has the working title Assail and will be set on that continent, and will also act as a coda to the main series. Esslemont also confirms that he hopes to get the books out a yearly intervals (so City in the Jungle in late 2012 and Assail in late 2013, hopefully).
The interview also features additional tidbits on how he and Erikson give feedback on one another's work, and his plans for a series of novellas showing the formation of the Malazan Empire. Interesting stuff.