the short answer is that we are stuck. at the energy levels we are at now, roughly 200 gev, we aren't able to learn anything fundamentally new. the LHC goes up to 7 or 8 tev, 40 times more powerful than the relativistic heavy ion collider.
It's an open question as to whether those 8 billion dollars would be better spent elsewhere. For instance, building the james webb space telescope is only 4 or 5 billion, half the cost of the LHC, and it seems to me you get more actual science out of a space telescope than you do a collider.
The problem with colliders is that to get to that "next level" the energies keep going up by an order of magnitude. So for instance, the cyclotron was only 15 mev and you could build one yourself in youro back yard, anti matter was discovered with a bubble chamber, basically a water cloud, then things like mesons were discovered with synchrotrons at 100's of Mev or sometimes a few Gev, and with each factor of ten or so, we would discover something new.
Well, now we are at the point where to go up another factor of 10 requires a tremendous amount of financial and engineering support, that's why it costs 8 billion.
If we want to do any particle science we have to spend this much. Is it worth it? Depends on who you ask. Ask a particle physicist he will say that's the only way he can do science. Ask an astronomer, you might get a different answer.