To be excruciatingly precise, the ONLY cable that is truly dmx is 5 pin twisted pair shielded. This according to the USITT standard updated a couple years ago.
4 pin scroller cable is not dmx, although it is used in lighting. As is 3 pin xlr, and perhaps 6 or 7 pin. Or cinch-jones. And all the others. Theoretically, 3 conductor extension cords could carry dmx data. So while it is possible that any cable carries a dmx signal it is not truly dmx standard unless it is 5 pin xlr twisted pair shielded cable.
Should anyone ever need to order 6pin XLR plugs and connectors, be aware there are two pin configurations, and they are not compatible with each other. One has the pins arranged symmetrically, the other does not. I believe the ETC RFU (Expression family) uses the non-symmetrical, and Telex and CLearCom use the symmetrical, but I might have that backwards.
What do we think about the possibility of ACN and data in general being delivered wirelessly inside a venue? No need to connect anything besides power. I see the clear advantages of wires over wireless whenever possible, but I think it'd be an interesting idea. This one is pretty stupid, but what if data and power were integrated into a single connector? That would be kinda weird...
Yeah, many people have tried power and data in the same cable for several different applications.
It's been touched on but not really clearly... The original purpose for those two extra pins was for information from the device to be returned back to the console. There are a few applications where this is going on right now but EXTREMELY limited.
As for the future of DMX. It is on the way out BUT it will be VERY slow. ACN and Ethernet based control is coming very soon. While we wait for ACN to be fully adopted we are in a period of proprietary ethernet languages. New Consoles have been coming out with both ethernet and DMX jacks for a year or two... I believe EOS is the first to ONLY have ethernet jacks (right?) I'm not sure what intelligent gear has ethernet jacks just yet but it won't be long until it all does. There are a lot of advantages to the user of ethernet based control, #1 being the cable is far cheaper.
My new theater is Strand based so it will "talk" Strand's proprietary ethernet language from the console to the dimmers and back. The Strand language goes out over the ethernet system of the theater to the DMX nodes. The nodes translate it into DMX and from there it's DMX cable to my gear. In the future my console and dimmers will be upgraded to speak ACN If I am able to purchase gear that speaks ACN there will be no need for the nodes, or the expensive DMX cable. Everything will speak ACN and connect via ethernet cable.
To me, the best part of the future is RDM. With RDM we will no longer need to set DMX addresses. The gear will identify itself to the network and talk back to the console. You'll be able to plug in a bunch of gear hit a button and it will all find itself in the network. Much like plugging in a USB device to your computer today.
When will we all have ACN? About the time Charc retires. ACN and RDM are realities that will be implemented soon. The technology is here and the manufacturers just have to go through the process of implementing it. However the question is, can your theater afford to switch when your DMX system is working just fine? Yeah that's what I thought. My guess is in about 5 years the vast majority of new purchased gear will no longer be DMX based. Gradually as systems go down ACN will replace DMX. So it'll take a good 15-20 years until most of us make the switch to ACN. Then it'll be another 15-20 years after that until the "cinch jones" club (little community theaters, schools, and churches) give up their ancient gear and upgrade to ACN equipment. DMX is dead technology... but she's going to take a REALLY long time to die so get used to her.