Quote from MTE:
A straddle/strangle is basically a bet that the realized volatility will be greater than implied, or, in other words, that the market has mispriced the straddle/strangle.
It is possible that one makes money with HV < IV, and also possible that one looses money even when HV > IV. The returns from delta hedging are path dependent; it is not enough to be correct about the relative pricing of IV/HV. On the other hand, if IV increases the accumulated profits from delta hedging can be quite substantial, assuming the trader has hedged rationally (1/2/3 daily sigma). The key to this strategy is accurate HV/IV forecasting, combined with disciplined delta hedging (no top or bottom picking or delta bias).
-segv