Maybe if the combattant nations push themselves even harder in the opening months, striving desperatly to salvage some sort of victory by the end of the year, we might have the makings of a peace of exhaustion? IIRC the logistical tethers of most of the armies were stretched to the limit by the pressure of modern warfare; if we see even more intense fighting, with all that implies (increased casualty rates, overworked supply trains, sapped morale), for more marginal gains, then perhaps around christmas time, somebody siezes on the symbolism and the truces become more widespread?