India generates approximately 0.16 million tonnes per day of municipal solid waste (MSW), of which nearly 10% is plastic, with a collection efficiency of 95.4%. However, only 13% of collected plastic waste is recycled, and 4% is treated in waste-to-energy (WtE) plants, while the remaining waste is unaccounted and openly burned along with MSW, resulting in greenhouse gas (GHG) emissions. This study presents a cradle-to-grave life cycle assessment (LCA) framework to quantify current environmental impacts associated with plastic production and waste treatment, along with future emission projections. Three scenarios: SC 1, crude oil extraction and plastic production; SC 2, open burning of plastic containing MSW; and SC 3, incineration in WtE plants, were considered under the system boundary. The results indicate that global warming potential (GWP) varies significantly across scenarios, with values of 403.29 and 1649.60 kg CO2 eq for extraction and production, 1520 kg CO2 eq for open burning, and 755.32 kg CO2 eq for WtE incineration. Furthermore, long-term plastic emission trends from 2023 to 2070 were projected using a linear regression model integrated with deterministic constraint-based allocation, aligned with India’s Net-Zero 2070 target. Three waste management pathways, business-as-usual, technology scaling, and waste reduction, were assessed. Under the business-as-usual, emissions increase from <1 million tonne CO2 eq in 2014 to nearly 30 million tonnes CO2 eq by 2070. Technology scaling reduces emissions by minimizing open burning, while waste reduction results in the lowest emissions, achieving ∼55–57% in GHG emissions. Overall, integrating LCA with forecasting and pathway optimization supports climate-resilient, sustainable plastic waste management strategies in India.