The Minifigure wave comes out globally in May (probably later here), to coincide with the 25th anniversary of the cartoon. (has it been that long already? It's amazing to think that it is only 5 years younger than Transformers)
The set of 16 figures will include - Homer, Bart, Lisa, Marge, Maggie, Chief Wiggum, Itchy, Scratchy, Mr Burns, Krusty the Clown, Milhouse, Ralph Wiggum, Nelson, Apu, Ned Flanders and Grandpa.
(they are probably the most significant 16, so will probably all be available in the build sets as well, just to cater to both completist and thrifty collectors)
Interesting to hear that the 25th anniversary episode will be a Lego episode... or at least one of the 25th anniversary episodes, as I read elsewhere that a crossover with Family Guy was to be expected as well.