In Jain Dharma, the idea of “next Tirthankars” must be understood carefully in terms of time‑cycles.

1. In our present time (current avasarpinī)

• We are in the descending half‑cycle (avasarpinī) in Bharat Kshetra.
• Bhagwan Mahavirswami is the 24th and last Tirthankar of this half‑cycle.
• No new Tirthankar will come now in this current avasarpinī in Bharat Kshetra.

So from today’s point of view, there is no “next” Tirthankar after Mahavir in our present half‑cycle. ( jainknowledge.com)

2. In the next half‑cycle (future utsarpinī)

• After this avasarpinī ends, there will be 5th and 6th ārā (very sorrowful times, no Tirthankars).
• Then a new ascending half‑cycle (utsarpinī) will start.
• In that future utsarpinī, again 24 Tirthankars will arise in Bharat Kshetra, in its 3rd and 4th ārā. ( jainknowledge.com)

About their names:

• First future Tirthankar of that next utsarpinī is traditionally called:

- Padmanābh – in many Digambar sources - Mahāpadma – in some Śvetāmbara references ( jainknowledge.com)

• For the full list of all 24 future Tirthankars, different later texts and traditions give slightly different names and details.

There is no single, fully agreed, scripturally certain list accepted by all traditions.

To preserve purity of Jain Dharma, it is better not to present a long, fixed list of “next 24 Tirthankars” as if it is 100% from original Jinvāṇī, because our main Agams do not clearly fix all those 24 future names with full details. ( jainknowledge.com)

3. Very simple summary

• Now: After Mahavir Swami, no more Tirthankars will come in this present half‑cycle.
• Later: In the next utsarpinī, again 24 Tirthankars will be born in Bharat Kshetra.
• The first of those is called Padmanābh (Digambar) / Mahāpadma (Śvetāmbara).
• A complete, certain list of all “next 24” names is not firmly established, so we should avoid guessing.

You can read more in simple language here and here