We consider the problem of robust asymptotic output regulation of nonlinear systems in the presence of generic unstructured nonlinear model uncertainties. Inspired by recent results establishing that this problem cannot be solved by a finite dimensional smooth regulator, we propose a new paradigm based on the use of linear infinite-dimensional internal models. As a special case, we consider the problem of output regulation in the presence of quasi-periodic signals, e.g. signals composed by a sum of periodic signals with incommensurable periods.