Although why are people who are using the bus to get to work not just buying a bus and tram pass anyway rather than relying on PAYG? Which then negates the need for an hourly bus ticket altogether - as thats who Khan is marketing this towards.
I would imagine the main beneficiaries would be:
1. Shoppers etc. or people making occasional journeys, or people commuting 4 or fewer days per week - who would at present be unlikely to have a bus pass.
2. People who currently have a bus pass in solely order to make a shortish commute 5 days/week involving a change of buses - since with the 'hopper' fare, it would become cheaper to just use PAYG instead of buying a pass pass.
3. Anyone whose journey could be equally well done either on one bus or by changing buses (and who doesn't have a bus pass) - since those people will then have a greater choice/frequency of route without having to pay more.
EDIT: Another variation would be - say - someone for whom one bus takes them to about half a mile away from where they need to go. If you have that kind of commute, you may well walk the half mile at the end of your commute to keep the bus fare down and/or avoid the need to buy a bus pass. But with a hopper fare, you then have the option of getting another bus for that bit of the journey instead, without having to pay extra.