ImageAT&T's Glenn Lurie believes that WiFi-only tablets won't be around for long as the cost of cellular modems falls. Talking at CTIA Wireless, the "emerging devices" honcho thinks that the low ($30) cost of an HSPA+ radio will eventually make manufacturers abandon the two-tier model -- doubling the potential customers for his network. He pointed to the success of the sold-out Pantech Element and has said that the company would be offering similarly enabled tablet devices in the future. Of course, if manufacturers only charged $30 extra for 3G-enabled tablets in the first place, we probably wouldn't be having this conversation.