If McCabe had the intention of sacking, why leave it until Wednesday? He would have got him there on Sunday or Monday to do the deed. Of course business commitments may have prevented this, but I'm sure he would've altered his schedule for something so important.
In my opinion, he either wanted to wait on the WBA result and decide after that, or he is issuing the final ultimatum to one or possibly both of them. All other departments of Sheffield United PLC seem to be working in a very succesful and positive way, but the football board are not operating in the same way. As chair of that, Robinson may well be being called to account for what is going wrong, as I understand things Robson was his choice (as was Brian Kidd, going against Warnock I'm led to believe) and he persuaded McCabe to by-pass the conventions of recruitment and not conduct interviews; and as manager Robson is ultimately responsible for what happens on the pitch.
I think a defeat tonight may be the end for him, but McCabe is intensely proud of the very different approach at SUFC to most other clubs and he may well give him more time. I don't buy the idea that the cup run may save him as I think McCabe has other priorities that will far out-weigh anything a cup run brings.
If anything happens, I anticipate a fairly major shake-up of things, with more than the manager being relieved of their duties!