  We forecast constraints on primordial non-Gaussianity (PNG) and bias
parameters from measurements of galaxy power spectrum and bispectrum in future
radio continuum and optical surveys. In the galaxy bispectrum, we consider a
comprehensive list of effects, including the bias expansion for non-Gaussian
initial conditions up to second order, redshift space distortions, redshift
uncertainties and theoretical errors. These effects are all combined in a
single PNG forecast for the first time. Moreover, we improve the bispectrum
modelling over previous forecasts, by accounting for trispectrum contributions.
All effects have an impact on final predicted bounds, which varies with the
type of survey. We find that the bispectrum can lead to improvements up to a
factor $\sim 5$ over bounds based on the power spectrum alone, leading to
significantly better constraints for local-type PNG, with respect to current
limits from \textit{Planck}. Future radio and photometric surveys could obtain
a measurement error of $\sigma(f_{\mathrm{NL}}^{\mathrm{loc}}) \approx 0.2$. In
the case of equilateral PNG, galaxy bispectrum can improve upon present bounds
only if significant improvements in the redshift determinations of future,
large volume, photometric or radio surveys could be achieved. For orthogonal
non-Gaussianity, expected constraints are generally comparable to current ones.
