One of my all-time favorite questions from the audience during a conference talk: I was discussing Y2K problems in date formats, I think in email message headers, and this attendee asked if my proposed practice, of using a 4-digit year, wasn't subject to Y10K problems instead.
There are two answers to that. One is that, in the context of a message header, there is nothing to stop you from going on to 5-digit years when the times comes. The problems intrude only if in the year 10000 you stupidly decide to roll over, odometer-style, to 0000.
But the larger answer is that it does not make sense to plan network protocols on an 8,000-year timescale. 8,000 years ago, we had invented fire and agriculture, but not writing. Metallurgy and metal tools were still works in progress.
Trying to predict the information technology needs of the year 10,000 is at least as silly as asking someone from the neolithic era whether message headers should use a 2- or 4-digit date format, and less likely to produce a useful answer.