SLE has left ET... not sure if he'll be back.
Are we talking about probability distribution, or IV curve?
Bi-modal distributions don't make sense in options... since the payoffs across strikes are all linked to each other. They are linear at expiration... Of course you can estimate the best strike to be long given a certain scenario, but that doesn't mean the calls at lower strikes don't pay out.
Of course you can have a very flat type of IV curve... but that doesn't mean the probability distribution is flat. That's usually in a very high IV across the board.
Or in case of very low volatility, everyone is trying to be short ATM and long wings... so you get a very smiley curve.
Skew can also reverse. OTM calls might have a higher IV than OTM puts. Depending on the scenario, that usually happens in the shorter term options. Long dated ones, especially when in an elevated IV, the calls will still be priced with a slightly lower IV than ATM/OTM puts. That's because eventually, when things normalize, IV should come down again. You would expect the "panic-up" will stop at one point. You want to be long the call spread then... Not just long any OTM calls.