It's very odd timing. To me you either sack him once we get to 40 points and say essentially he has done his job. It would have seemed ruthless but also a very clear message to the wider footballing world Allardyce was solely here to keep us up and we are not to see ourselves in that loop.
Or you sack him after a big defeat (like Arsenal). Or you then wait until the end of the season. I'm not sure what's gained by giving Unsworth another 5 games, or worse still another manager 5 games with a terrible squad to work with at the end of an awful season.
It will be a terrible end to the season, lots of anger and frustration by fans. Allardyce currently is centring a lot of that and taking a lot of the heat for it. He's playing a useful purpose. I don't know why that doesn't continue.
The bets case in this, is you do a City, announce Fonseca comes in the summer and Allardyce will leave. We seem to be jumping the gun again a bit though, and if we don't appoint someone or have someone lined up and out Sam, it does run the risk of becoming a circus again. (In Hindsight Koeman should only have gone once agreement was reached with Watford re Silva).