Year 2038 problem and year 2106 chain halting

The discussion in this thread revolves around the potential issue of the year 2038 problem, where the chain may halt for all old clients due to the lack of a 32-bit value greater than 0xffffffff. The three rules currently in place regarding block timestamp are discussed, and it is suggested that an additional rule could be added requiring a 64-bit (or larger) timestamp in the coinbase transaction. A similar scheme could potentially be used for nLockTime as well. It is noted that if changes such as these are made in the next five years, it will still be over a decade before any wrapped-around timestamp is legitimately mined, which seems unlikely considering the pace of consensus changes. Testing shows that there does not seem to be a timestamp that can be used in any next block and accepted by old nodes.