Fossil fuel divestment has quickly become the largest divestment campaign in history, drawing attention to the large discrepancy between national climate commitments and the continued support of the fossil fuel industry. Yet, fossil fuel production and emissions continue to escalate rapidly. Our question is: what's next for the divestment movement? We propose a conceptual framework that identifies two waves of divestment leadership in which public pressure campaigns move towards targeting the extractive economic structures and predatory behaviors that permit fossil fuel extraction, and unsustainable resource extraction more generally, to continue without limit. Building on the three waves model of divestment, we postulate that a fourth wave of fossil fuel divestment organizing has already begun, one that focuses on banks, insurers, and other financiers of fossil fuel projects. Further into the future, we envision a fifth wave of divestment campaigns, whereby divestment is used in climate and environmental activists' arsenal to target firms that engage in environmentally damaging and unjust behaviors such as destructive mining activities, overconsumption, predatory debt or arbitration processes, or Indigenous rights violations. While divestment is not a panacea and does not displace the work of existing post-extractive or climate justice campaigns, we argue that divestment is a powerful tool that can be used to complement and amplify the work of environmental justice activists in other contexts beyond fossil fuels. This paper offers actionable suggestions for current and future activists and frames divestment as a tactic that will proliferate within other environmental movements in the transition towards a post-growth economy.