[qwerty123]

I can see the new presenters doing longer hours than currently

Not necessarily - assuming Outside Source is still kept on at 7pm, the daytime 5am - 7pm weekday schedule can still be broken down into 4 x 3 hour and 1 x 2 hour shifts.
The main unknown is what shift Christian Fraser will do - whether he'll stay on The Context for an hour at 9pm or if he'll be moved into the weekday daytime schedule.
If he does stay on at 9pm, we could have a presenter/reporter doing a weekday daytime shift.

I suspect Christian will stay on evenings but may well incorporate OS into his slot. I think the 5am shift is by far the most likely to be covered by a reporter-presenter as arguably it has essentially been a business slot with a bit of news rather than the other way around for a number of years to the extent that regular cover is provided by the business rather than news team including on occasion by people who would never appear on the main news at any other time of day (it is also notable that none of the seemingly informed articles have listed Sally amongst the departures).