Canonrumors has posted the supposed specs for the t4i. Some bullet points.
18 MP APS-C
SDHC slot, USH-1 complaint
Current xxD’s AF system (9 cross-type points, found in 40D, 50D, 60D)
T3i metering system (63 zones like 7D and 5DIII)
ISO 100-12,800 expandable to 25,600
Articulated touchscreen LCD
Hybrid AF during video shooting