  In this article we discuss the role of current and future CMB measurements in
pinning down the model of inflation responsible for the generation of
primordial curvature perturbations. By considering a parameterization of the
effective field theory of inflation with a modified dispersion relation arising
from heavy fields, we derive the dependence of cosmological observables on the
scale of heavy physics $\Lambda_{\rm UV}$. Specifically, we show how the
$f_{\rm NL}$ non-linearity parameters are related to the phase velocity of
curvature perturbations at horizon exit, which is parameterized by
$\Lambda_{\rm UV}$. Bicep2 and Planck findings are shown to be consistent with
a value $\Lambda_{\rm UV} \sim \Lambda_{\rm GUT}$. However, we find a
degeneracy in the parameter space of inflationary models that can only be
resolved with a detailed knowledge of the shape of the non-Gaussian bispectrum.
