With those assumptions, yes.
Assuming a historical perpetuity-appropriate rate of return (3-3.3%), about 850,000 to 925,000 USD are needed to cover medical costs for a family of three for an indefinite period of time, if one conservatively estimates that Max Out-Of-Pocket will be reached every year.
One of the more interesting exercises I did was to look at the cost of plans with a low Max Out-Of-Pocket, and a higher monthly premium. Oddly enough, they worked out to very roughly the same annual cost. Gosh, it's almost like they had someone really good at statistics and case optimization building their numbers.
In my case, since we are all in overall reasonably good health compared to others in our age groups, we decided to carry much of the risk ourselves and let the insurance cover the more catastrophic cases, under the assumption that we would normally not approach the Max Out-Of-Pocket limit every year. We pay for the Bronze level coverage, and make a maximum contribution to our HSA every year.