Relevant to this thread, let me introduce GO's older BiLevels, nearly all of which are still in service today.
(
source)
1978 photo, coach number 2056 on its side,
still in service today -- I saw it recently.
This was displayed at the Ex on August 29th, 1978, and
TransitToronto's page on this coach is quite interesting reading on the history of these coaches.
These coaches and cabs are still being made today, so it's possible some of the newer ones rolling off the assembly line could possibly last to the
second half of this century. Either on one of the other North American commuter lines, or even locally on an unelectrified line (Richmond Hill, Niagara, etc) or pulled by electric locomotives.
One of the first non-prototype GO coach, #2001, is still in use today, running as part of another city's commuter train service, having been sold off during GO's cutbacks in the 90s.