The potential of Er-doped Cs2NaYF6 and GaN for mid-infrared emission at λ≈ 2.7 ν is investigated using time-resolved optical spectroscopy. This emission results from electronic transitions between the second (4I11/2) and first (4I13/2) excited states of the Er3+ ion. By recording the photoluminescence transients for the 4I11/2 → 4I15/2 and 4I13/2 → 4I15/2 transitions after pulsed excitation, we determine the lifetime of the 4I11/2 level and demonstrate that the 4I13/2 state is populated from this level. Our results indicate that both host lattices should enable 2.7 νm emission, which is temperature-stable but subject to concentration quenching.