As Mr. Drouin mentioned earlier, probably the biggest answer to the problem of packaging-related pollution is to get away from single-use packaging altogether. It's less of a material question than an infrastructural system question.
What concerns us about continuing to use plastic for packaging is the chemicals I mentioned and the propensity to create microplastics. Reuse and refill systems can use any other type of material that exists today, but the big challenge will probably be more of a process engineering type of challenge than a material science type of challenge, I suggest.