FFXIII will have to come out in SE's fiscal year,which ends march 31st 09.If you look at their recent 08 FY report,you'll know why,but i can imagine FFVXIII coming out late next year,why?
FFVXIII started development around the time KH 2 wrapped,so not to long ago.
FFXIII stated development around when FFX wrapped.Which is the reason why FFXII was developed by an entirely diffrent studio;so that SE could release FF's faster and allow the main FF team to work on XIII in the time being.
If there is no info at E3,then their is a cause for concern.