  Combining the measured B_s mixing with b \to s\ell^+\ell^- rate data, we find
a sizable 4 generation t' quark effect is allowed, for example with m_{t'} \sim
300 GeV and V_{t's}^*V_{t'b} \sim 0.025 e^{\pm i 70^\circ}, which could underly
the new physics indications in CP violation studies of b \to s qbar q
transitions. With positive phase, large and negative mixing-dependent CP
violation in B_s system is predicted, \sin 2\Phi_{B_s} \sim -0.5 to -0.7. This
can also be probed via width difference methods. As a corollary, the short
distance generated D^0-D^0bar mass difference is found to be consistent with,
if not slightly higher than, recent B factory measurements, while CP violation
is subdued with \sin 2\Phi_D \sim -0.2.
