There was a time when the d6 system was as popular as any on the market. Games like Star Wars, and Ghostbusters were critically acclaimed. It was an easy system to learn, and it thrived.
I don't want to paint the picture that everything was rosy; we know the old West End Games had troubles, and of the scattershot, uneven history of d6 for more than past decade. Many of us also became extremely tired of the uncertain nature and on again/off again changes and plans of Eric Gibson's WEG for the past two years, and took a bit of a break from considering or thinking about d6.
I don't want to relive the past, but d6 was already pretty minor when people thought about generic systems, having been eclipsed by active, well-supported systems such as Savage Worlds. But there's still a fan base out there that knew about d6, and probably played some Star Wars back in the day. And now we have Open d6, and resultant projects such Mini Six, which I think is the cleanest version of d6 we've had in quite a bit.
But what else is going to come out of Open d6? Looking here, we can see there's a lot of folks planning to create products for 2011. How far it'll go, who knows, but I have to be encouraged that as many people as are listed even want to try.
I think it's going to be very interesting to see if projects like the D6 Magazine that's been floated about or the dark fantasy RPG Destiny6 have legs. Those might be good bellweather indicators.
So, I don't know. I don't think d6 is going to take over the hobby, but I don't think it's quite finished yet. Obviously, judging from the forums, it still has a dedicated core, perhaps not unlike FUDGE or Fuzion. To see if it goes past that is up to the creative minds of the Open d6 movement, and just how active they are, and what sort of audience they're able to pull back in.