In Jain tradition, Shri Krishna is associated with the 12th future Tirthankara of the next Utsarpini, named Shri Amam / Amama. Some Jain texts and summaries also state this as the soul of Krishna becoming Amam, while traditions may show minor spelling differences. ( jainqq.org)

So, the short answer is: he will be Amam (Amama), the 12th future Tirthankara. ( jainqq.org)