Lemonstein said:
Certainly anyone who'd watched and paid attention to the OT would have known that back in 1999.
Not true - the name "Palpatine" is never said once in the OT. Without things like the close up on Palpatine at the end of Qui-Gon's pyre, all the audience would have been able to guess is that Sidious and the Emperor are one in the same, but not that Sidious and the Emperor and Palpatine are.