The latest determination of the extragalactic gamma-ray background (EGRB) radiation
by Fermi is compared with the theoretical prediction of the blazar component by Inoue
& Totani (2009; hereafter IT09). The Fermi EGRB spectrum is in excellent agreement
with IT09, indicating that blazars are the dominant component of the EGRB, and contributions
from any other sources (e.g., dark matter annihilations) are minor. It also indicates
that the blazar SED (spectral energy distribution) sequence taken into account in
IT09 is a valid description of mean blazar SEDs. The possible contribution of MeV
blazars to the EGRB in the MeV band is also discussed. In five total years of observations,
we predict that Fermi will detect ~1200 blazars all sky down to the corresponding
sensitivity limit. We also address the detectability of the highest-redshift blazars.
Updating our model with regard to high-redshift evolution based on SDSS quasar data,
we show that Fermi may find some blazars up to z~6 during the five-year survey. Such
blazars could provide a new probe of early star and galaxy formation through GeV spectral
attenuation signatures induced by high-redshift UV background radiation.