If you've read any articles on the Playbook, you'd see that the first models will have wifi only. Later models will have 3g/4g. PlayBook Coming April 19, Available for Preorder at Best Buy - PCWorld
The PlayBook available for preorder at Best Buy does not have a 3G option, but RIM is expected to unveil 3G + Wi-Fi and 4G + Wi-Fi versions in the future. In February, RIM said 4G PlayBooks would arrive during the second half of 2011 for LTE networks such as Verizon's, HSPA+ networks such as AT&T's and WiMax networks such as Sprint's.
This is the same as what sites have reported.