e.g., refs. [@Carlos01] and [@Fogli3nuSNO2KamL; @VitoAKamL02] and the articles quoted therein). Combining the data from the solar neutrino experiments and from KamLAND would permit to determine $\tan^2\theta_{\odot}$ with a high precision as well: the estimated (1 s.d.) error on $\tan^2\theta_{\odot}$ is [^8] $\sim 5\%$ [@Carlos01].

Similarly, if ${\mbox{$\Delta  m^2_{\mathrm{atm}}$}}$ lies in the interval ${\mbox{$\Delta  m^2_{\mathrm{atm}}$}}\cong (2.0 - 5.0)\times 10^{-3}~{\rm eV^2}$, as is suggested by the current atmospheric neutrino data [@SKatm00], its value will be determined with a $\sim 10\%$ error (1 s.d.) by the MINOS experiment [@MINOS] which is scheduled to start in December of 2004. Somewhat better limits on $\sin^2 \theta$ than the existing one can be obtained in the MINOS experiment [@MINOS] as well. Various options are being currently discussed (experiments with off-axis neutrino beams, more precise reactor antineutrino and long base-line experiments, etc., see, e.g., [@MSpironu02]) of how to improve by at least an order of magnitude, i.e., to values of $\sim 0.005$ or smaller, the sensitivity to $\sin^2\theta$.

All the indicated developments are expected to take place within the next $\sim (7 - 8)$ years, i.e., by 2010. We will assume in what follows that the problem of measuring or tightly constraining $\sin^2\theta$ will also be 