A 4th generation scenario
  A fourth generation could provide, within SUSY, a solution to baryogenesis at the EW scale. It is allowed by precision measurements. Available data from Tevatron already restrict the allowed domain of parameters for the new quarks and the Higgs boson. There are some indications from b->s transitions which could be interpreted within an extension of the CKM matrix to 4x4, in particular CPV in the Bs time-dependence for the J/Psi-Phi mode observed at Tevatron. If confirmed with more data the 4MSSM interpretation predicts a very interesting scenario for LHC and a TeV LC. 
Francois Richard