Dual-SIM models are usually not seen in the U.S. and are more often used overseas where it allows the same phone to be used for two different lines. The Motorola Moto X front plate shows two SIM slots labeled SIM 1 and SIM 2. Also leaked is a picture purportedly showing off the back plate of the Motorola Moto X in three different colors. Note how the placement of the speaker on those three cases is on the opposite side of than where the speaker is located on the dual SIM model. That could indicate that there will be some physical changes between the two variations of the phone, besides the second SIM tray.
With no Motorola media event scheduled for this week, you can expect to see more speculation about the Motorola Moto X and the Motorola DROID Ultra models.
Leaked pictures of the Motorola Moto X
source: NWE (translated) via AndroidCommunity