Short answer:

• In our Bharat Kshetra (this world) during the current avasarpini, there will be no “next” Tirthankar after Bhagwan Mahavir. He is the 24th and last of this half‑cycle.
• A currently living Tirthankar exists in Mahavideh Kshetra: Shri Simandhar Swami.
• In the next time half‑cycle (utsarpini), new Tirthankars will appear again. The first will be known differently by tradition:

- Digambar: Padmanabh - Shwetambar: Mahapadma (Tradition mentions his father as King Shreedhar.)

For simple reading on these points:

• Living Tirthankar: Simandhar Swami
• No Tirthankar now in Bharat Kshetra; future cycle understanding
• Next utsarpini first Tirthankar (Padmanabh/Mahapadma) note