Required number of bits in nonce Is there a formal proof that with N bits to iterate in the nonce of the block, a hash satisfying proof of work will be ever found?

How large that N (number of bits in the nonce) should be to satisfy proof of work in 10 years, 100 years?
In addition to the 32-bit nonce in the block header, miners can also update the extraNonce of arbitrary length in the coinbase transaction to get a different merkelRoot, so that a proof of work hash can always be found.