Regardless of whether COVID-19 resolves quickly or not, further declines in marriage rates are all but guaranteed.
Wealth and income inequality has gotten so bad in the US that it is now possible to make a compelling argument for progressive policies and a robust welfare state on the basis of goals previously considered conservative (goals like encouraging procreation and family cohesion). Individuals correctly identify the costs of marriage and having children and choose rationally to avoid incurring those costs, or are simply unable to incur those costs in the case of homeownership. As rents and other costs of living exacerbated by having a family continue to balloon, it's only a matter of time until the upper middle class begins to suffer the same effects.
A progressive think tank called People's Policy Project has thought up the Family Fun Pack (https://www.peoplespolicyproject.org/projects/family-fun-pac...) to address exactly these problems, though currently its support among elected politicians is mostly nonexistent.