How many new elementary particles will the LHC discover?

Seven and a half? Negative two?

No one knows how many there are to find because they haven't found them yet. There's no tech tree in this videogame; you can't look at the manual and peak at all the technologies you haven't researched yet.

Some scientist suggest that there is more and more particles with higher and higher mass so there is no limit to the number of particles yet to be found
                                         Graviton and the higgs boson would be the most important particles that would be found

Nothing yet, the most important would be the Higs Boson, which is a supposedly fundamental particle, which means you cant get smaller. For eg atoms are made of quarks but a higs would not get any simpler that would be it. If discovered it would be by far one of the most important discoveries in physics in a while.

The Higgs boson, thought to be responsible for mass, is the particle everyone's talking about.  If the LHC provides evidence for Supersymetry, the number of known particles will double though I'm not sure you could say they'd been "discovered".

I have a bet with someone that the Higgs will *not* be found, but that they do find at least one supersymmetry candidate.

I'll explain. Suppose the LHC finds the HIggs. Then some people, including Peter Higgs, will get a Noble Prize. But we haven't learned anything new as this is the scenario that everybody expects to happen.

On the other hand, the Higgs particle is essential. Not so much because it gives mass to particles, but because it keeps some infinities out of the calculations. So if it doesn't exist, then there should be something new going on around 1 TeV particle energy. And it  would be much more interesting to find that.

Totally agree with ronwizfr. The classical Higgs would be a bore and would not teach us anything. The theory which accommodates it is around since the end of the sixties. It is, of course, far better than what preexisted, but it is not satisfactory. And the only way to see beyond is not to find the standard Higgs, but maybe indications of some dynamical symmetry breaking mechanism which would dispense us with the Higgs, or at least the Higgses of the MSSM (minimal supersymmetric standard model)
Should this latter hypothesis turn out to be the good one, the answer to your question would be at least a doubling of all the elementary particles which constitute the SM (at least in principle, because we would know that supersummetry exists in Nature. It does not mean that many supersymmetric particles would actually be 'seen' at LHC)

I hope they something that will stop my Computer crashing.

If anyone knew what would be discovered by the LHC, there would be no point in building it.