We've had all waves released here of all size classes except Deluxe (see the sightings box in the header above)... and the tail end of a toyline is always unreliable, so if there aren't future waves of other sizes available to sell with wave 3 & 4 Deluxes, some Retailers (like Kmart) probably didn't want any more of a Toyline that is now "completely released" in four of the five size classes (POTP was only meant to last 12 months, and it has now been 9... Hasbro has probably scheduled it this way to give Retailers 3 months to clear the shelves for the next phase - WFC).
According to Hasbro in the wave 2 news topic, they have more Deluxe toys expected in November... but don't expect it to be released to all stores, or even at all. Retailers may cancel in favour of the Bumblebee Movie toyline, or if the Movie toys don't sell enough when they are released in October. Or, the POTP Deluxes could be a special import for a pre-Christmas sale at just one particular retailer (like BigW getting all of the wave 2 & 3 POTP Leaders, and a big bulk order of cheap Titans Return toys).
Unfortunately Kmart are pretty reliable when it comes to Clearance tags... in that it means that they are done with that product code (size class), and when that stock disappears from that store, there won't be a restock.