Possibly. However, the analysis will be different Under an EP analysis--the court would need to determine the level of scrutiny to apply to the EP argument (strict scrutiny (the highest), intermediate scrutiny or rational/reasonableness). I suspect that the court will find that there is no fundamental right to marry multiple spouses, thus, a law banning plural marriages (thus, discriminatory to polygamists that hold a sincere believe in plural) will likely have the rational basis scrutiny or the lowest scrutiny. A lot passes through this scrutiny level.
The state would argue that it has an interest in preventing a plural marriage for: (1) a regular and orderly system of property ownership, taxation and a system of descent & distribution (how intestate property is disbursed, which happens a lot). Second, there is a long history of abuse/predatory abuse to woman in plural marriage. Further, in plural marriage colonies, young males born in the community are ostracized and abandoned. The state has an interest in protecting these people.