In Jainism, there are 24 Tirthankaras in each half-cycle of time. Mahavira is the 24th and last Tirthankar of the current half-cycle. Therefore, there is no “next” Tirthankar today. When the cosmic time-cycle completes this half-cycle, a new cycle will begin and a new Tirthankar will arise in that future era.

If you’d like, I can list all 24 Tirthankaras in order or share how Digambar and Śvetāmbara traditions describe them.