There's that much conjecture about what dark matter/energy is that for the most part the best thing they can say is they don't know what they're looking at or really understand it. Yes, there are some reasonable hypotheses being suggested and I think the next decade of results from the LHC will bear out whether supersymmetry might be a deciding factor, or not, but that's for experimentation to decide. It's one thing to hypothesise the existence of supersymmetric particles through theory but it's something entirely else to actually produce the results empirically. I'd say given the track record of particle physics, they may find them (or they may have to ramp up the LHC's beam intensity further to find them), but you never know until you actually do the experiments at the proper energies. I wouldn't entirely rule out some form of baryonic matter either but I'm not going to hazard a guess as to what it might be for certain. I have a feeling that this question isn't going to go away for quite some time, yet. Not until we can actually sample or detect with certainty what's there.
As far as other theories go, interstellar magnetism/electrical fields, interactions with higher dimensions, modifications of Newtonian gravity, etc etc etc, they'll have to live or die on their merits through further observation and testing. For all we know, it might be a combination of factors which produce the results that we see. Sometimes, Occam's Razor doesn't cut properly because it's blunt
