RIG's logic is very good.
As a reminder, last year the games were on Saturday, Sunday (2) (we had the 3.30 slot) and Monday.
Premier Sports may well take Hearts v Rangers on Saturday. It would make sense for St Johnstone v Celtic to be on Sunday at 12.30 and for our game again at 3.30 Sunday. With the other Semi Final at Motherwell or St Mirren so the organisers would hope Kilmarnock get through for which for them would be a local derby at either. If Aberdeen got through, they would be livid at a Monday night slot.
If we get say a 7.45 evening kick off the organisers will assume 14,000 Hibees and 500 at most ICT supporters. I can now therefore see Friday night as an option but as CaleyD says 'TV companies will dictate'. Waiting until Thursday morning next week to confirm the arrangements would be pretty late. Last year we had details on the 14th February 2019 and our game was on the 3rd March. Must be a good chance of an announcement later today.
We are not TV companies but just fans so do not be surprised if we get a poor slot.