Hmm... people have been missing out a few points, but there are still other spartans.
As far as we know, Kelly, Linda and Fred are trapped in the shield world with several spartan 3's, grey team is unacounted for, as are the spartens from halo wars, but they may have met up with the rest eventualy somehow. All of gamma company is unacounted for near enough.
But, there is also the head hunters that are unacounted fully for, as well as the top honours group from Beta company, we know Noble are the top honors for Alpha, what else would they be?
There are also the rehabilitated sparten II's as well.
SO over all, there are alot of spartans left for the grinder.