  We explore cosmological consequences of two quintessence models in which the
current cosmic acceleration is a transient phenomenon. We argue that one of
them (in which the EoS parameter switches from freezing to thawing regimes) may
reconcile the slight preference of observational data for freezing potentials
with the impossibility of defining observables in String/M-theory due to the
existence of a cosmological event horizon in asymptotically de Sitter
universes.
