The claim does not specify that this ranking is by nominal GDP (current prices) rather than by purchasing power parity (PPP). By PPP, India is already the third largest economy.
Sources
PrimaryIMF World Economic Outlook Database (October 2025)India GDP: 4.51 thousand billion USD; Japan GDP: 4.46 thousand billion USD; Germany GDP: 5.33 thousand billion USD. India surpasses Japan to become 4th largest economy.
SecondaryTimes of IndiaIndia to become 4th largest economy in 2025 overtaking Japan according to IMF's World Economic Outlook April 2025
SecondaryCNBCIMF data projects India's GDP to reach $4.187 trillion in 2025, marginally surpassing Japan to become the fourth largest economy