I think it's a whole mix of things. Hasbro, retailers, modern kids, the economy and the political setting of the world.
• Hasbro—by my best educated guesses in actually knowing how to advertise shit (because my job has been "advertising shit" for the better part of a decade)—has majorly dropped the ball. There's barely a media tie-in with the toys, and when there is, it's ill-timed and never lines up with the release. I'm talking MONTHS apart, not weeks. They also don't seem to know how to leave something alone long enough for it to take effect. This is in part due to...
• Retailers. They want some hair-brained "core group" of characters, despite that being quite boring to always have the same 6 guys on the shelves. And of course, Hasbro reinvents the line every 6-18 months. They even do this with Transformers, which is strong enough to hold out likely because the media tie-ins are timed to coincide with the toylines, plus the movies have done REALLY well despite being pretty much awful stories.
• Modern kids are half-fucking-retarded. They have zero attention span, and the web and mobile gadgets don't help. They couldn't give two half-shits about story (or reading real books) and don't seem to be very creative or imaginative as a whole, and video games seem to trump our childhood staples of action figures, comic books and playing outside.
• The economy is shit. Well, it's crawling out of it, but it's still been pretty nasty. Combine that with gas prices, and plastic toys have taken a huge hit. Not to mention the prices are at that $9.99/+$10.00 threshold where moms stop buying single action figures, and, well, there you go.
• Then we've got the political setting of the world. In Reagan's 80's, it was bad-ass to be an American kid. The Cold War made us out to be the saviors of freedom. Now, post-9/11, we're the douchebags to the rest of the world, and war toys aren't exactly the thing that seem to be selling well.
Plus, shit changes.
Personally, I think G.I. Joe's not quite done yet. But if they want it to survive, they need to plan shit out for a 2-3 year arc, and not give up on it and change it 2-3 times in-between. Of course, this would require the suits and retailers (read: old, already-rich board members) to give a shit, and they don't... They want to make a quick buck and cash out, not keep a silly army brand alive for any length of time so it's profitable down the road for someone else. And they need a media tie-in that's actually fucking remotely tied-in. Not missing the mark by 9 goddamn months by being ridiculously early or late, and then under-produced or mis-distributed. And advertise! Jesus Christ, how hard is that? I'm not talking using a maximum budget, but commercials during popular TV shows with a similar demographic if they can't seem to run an animated series for any length of time to draw kids in.
And I think that they can reinvent the core characters from ARAH while peppering in some non-silly nostalgia to draw in us old ARAH fags. I mean, if we get our kids to watch it, what's the harm in that? It's already a built-in audience and a source that won't require as much farming to get our kids onboard. And they need more characters besides the usual suspects. The thing that I think doesn't work about Sigma Six, Renegades, TF: Animated or TF: Prime is that the teams are SO small, that they suffer from a lack of characters. I'm not talking about losing character development just to have a slew of faces in, or having the gallery of characters from ARAH, but 5 team members? The thing I always loved about the X-Men, TMNT, G.I. Joe, Transformers, etc. as a kid was that they had a basic group that were in nearly every episode, but they alternated in returning support characters all the time. Not to mention a decent rogue's gallery. And it doesn't mean that the team has to stay the same over 2-3 years... Just don't reboot it and start from scratch every season. No wonder Renegades didn't do any better than it did... Getting dropped before Season 2 could carry on the story and before any season 1 characters made it into stores probably did as much damage as postponing the Joe flick another 3/4 of a year after releasing the toys this May.
If they don't do something soon, though, it's dead in the water. And I mean, soon. Otherwise, they're going to need to bury it and wait 5 years for people's memories to fade and try bringing it back again, or leave it dead and call it done.