You may remember that during the lead up to this year's Mobile World Congress in Barcelona, one of the devices we were expecting from HTC was a quad-core tablet codenamed Quattro. HTC had, by most accounts, a very successful show, introducing the now-popular One series of phones. But Quattro -- which eventually became Vertex -- was nowhere to be found. It doesn't seem like there are any new tablets on the horizon from the Taiwanese manufacturer, either. Is HTC done with this product category? Are the Flyer and Jetstream the only two Android tabs that will ever see the light of day? ...