As far as I know, the largest land is 64 * 64 in Windenburg. EA, is it possible to provide a 100 * 100 size land for Sims builders to create even larger projects?
As far as I'm aware, 64x64 has always been the biggest available lot size throughout these games. A 100x100 lot would be absolutely massive and with the sizes of the worlds we're getting right now for TS4 it seems unlikely they'd include it. I agree we need more of the bigger lot sizes though. Building tends to get a bit cramped otherwise.