In Jainism, Ravana is not considered the next Tirthankara.

Ravana is generally described as a Vidyadhara king and a powerful person in Jain narratives, not a Tirthankara. The 24th and last Tirthankara of this avasarpiṇī was Bhagwan Mahavir.

If you mean the next Tirthankara to appear in the future, Jain tradition says it will be in the next utsarpiṇī, beginning with Padmanabha.

So, in short:

• Ravana = not a Tirthankara in Jainism
• Next Tirthankara = Padmanabha in the next time cycle

If you want, I can also explain Ravana’s role in Jain Ramayana tradition.