The Lynx dongle can be reflashed to output 1 universe of pixelnet data. No extra hardware required. The etherdongle is a new device that gives you 4 universes, so it is at least as good as four dongles, plus it connects via Ethernet (not USB) and looks like it will have other new features.
The 16 port Smart string/pixelnet hubs do have dmx output, but it costs you some of your pixelnet data (512 channels) so yeah you can get pixelnet and dmx from the one dongle if you have at least one hub.