Two is iPad 2.
I'm going Verizon here as there are only three SKUs. Adding the modem and RF circuitry would be fairly easy.
Either that or iPad 2 is coming earlier than thought. If it was iPad 2 though there should be six SKUs. That is three WiFi and three cellular enabled.
If the models are Verizon enabled it might mean iPad 2 is a ways away. Or it could mean that Apple intends to offer up the current iPad as the low cost lead in. The timing here is awfully strange though.