Actually Ismaila was one of the rotating hosts, so the audience  had the opportunity to hear him various times already for a few weeks.  This would likely be part of the audition and process of evaluating potential hosts.  

I saw him a few times during the shows hour TV simulcast on CBC Toronto in the morning.   He is a little more outgoing and I would say pleasant or happier on air than Matt tended to be.  David Common was pretty good as well when he hosted.

August 24 is a few weeks before the summer ratings come out and gives the CBC a bit of a chance to promote the new morning show and host for the fall book. Often when a station changes  format, especially something big like a morning host or music it sometimes comes right before or around the Labour Day weekend. 

Interesting to note that John Landecker's first show on CFTR was on August 24 1981.