I would not expect them to change their minds any time soon.
I would guess that the st-e4 arrives once rt flash master mode is available in the camera bodies, i.e. 5d4 or maybe 7d2 - imho this would have been a real valuable addition to the 6d: They can add 2.4ghz wifi, but not rt?!
If the st-e3 is obsoleted then Canon needs a new reason for customers to buy additional equipment, i.e. the version with af beam and maybe e-ttl3 with remote 2nd curtain sync for the upcoming 660rt flash :-p