Was at Kennedy to transfer to the RT, on the way up there didn't seem to be any sign that there is a Line 5 to transfer to inside the Kennedy station, must have missed it.
Instead of upgrading Line 5 in the future an alternate heavy duty line could approximate its route, like a GO Midtown line, particularly if it’s a TTC line.
They are yet to make it up since it's not known what would be needed at the time, especially to see how GO RER works out which could render some route picks redundant.