Remaining Potential Experimental Particle Physics Discoveries at the TeV Scale? With the discovery of the Higgs Boson, some have been calling it the end of experimental particle physics for our generation, due to the fact that all of the particles predicted by the standard model have been found (the W and Z Bosons in 1983 and the Top Quark in 1995) and no new physics is expected at the energy ranges we can probe. I have also generally heard from my friends who work in experimental particle physics (or, at the very least, accelerator physics) a similar story, that there isn't too much left to be discovered. 
Is this an accurate assessment? 
What about dark matter particle models, like the axion/axino? Can the LHC (or SLAC, etc) probe enough of a range to perhaps shed light on this cosmological problem? 
Can we hope for any more insights into beyond the standard model theories from current accelerators?
 A: The trouble with this question is that there is no strictly objective answer... only time will tell. How would we ever know what there is left to be discovered in any situation? Only after making a discovery do we know that there was one to be made in the first place...
We have a Standard Model of Particle Physics that describes existing measurements very well. There are processes that are predicted by that model that have not yet been observed, and it is a very reasonable expectation (possibly shared by everybody...) that these predicted processes will be discovered in upcoming data as predicted. So there's work to do on this front.
Then there's the search for really new processes, in the sense that they are not predicted by the Standard Model of Particle Physics. Everybody's guess as to how may of these discoveries (or indeed any) will be made at the LHC. For sure it's not getting any easier.
For a particular dark matter model, there will usually be one or three particularly well-suited experiments to conduct to test it (i.e. to try and discover it, if it exists to be discovered). You mention axions in particular, there are a good number of dedicated experiments searching for those.
But even if an experiment isn't perfectly suited to do a given measurement, once the experiment exists, one should of course still analyze its data to get the most out of it and see whether one can e.g. make statements about axions using LHC data. That is indeed an active area of research too.
Finally, to address your last question, that answer can certainly be answered positively, if only because no-observations rule out parameter space where beyond-the-standard-model-theories can live, and thus still provide a bit of insight even in that case.
