Two more waves of Rescue Bots "Rescan" bots have been listed on Entertainment Earth, but no images yet.

And in the process of compiling the list of recent waves, I realise that I've been confusing myself with the two red Optimus trucks from waves 17 and 18. I thought it was the same Optimus, which was the one with the Blurr/Trailer box set, but that was wave 18 Optimus. The wave 17 Optimus is a new mould, based on the appearance of the first "Megabot" Optimus that had the trailer that could become wings on the back of the robot (and then released on its own a year later). It is this wave 17 Optimus that has been showing up at stores here in the last couple of months, and only comes with older toys (blue truck Optimus, jet Bumblebee, dragon Heatwave and Brushguard) and the Chase SUV that was originally released with a trailer.
The wave 18 Optimus that comes with the racecar Heatwave and three older toys, has green stripes and was released with Blurr/Trailer, and has not been found here yet.

Wave 15 (wave 2 from 2017)
new - Bumblebee (jet)
new - Tango Heatwave (dragon)
new - Bumblebee Night Raptor
new - Optimus Night T-Rex

Wave 16 (wave 3 from 2017)
new - Chase (stegosaurus)
new - Optimus (blue truck)
old - Blurr
old - Medix
old - Hoist

Wave 17 (wave 4 from 2017)
new - Optimus (red truck - based on Megabot Optimus)
new - Chase (SUV - from the trailer version)
old - Tango Heatwave (dragon)
old - Brushfire
old - Optimus (blue truck)
old - Bumblebee (jet)

Wave 18 (wave 1 from 2018)
new - Heatwave (race car)
new - Optimus (red truck - from the Blurr/trailer version)
old - Chase (police car)
old - Brushfire
old - Boulder (bulldozer)
old? - Bumblebee (unknown version)

Wave 19 (wave 2 from 2018)
new? - Blades the Flight Bot (jet?)
new? - Classic Bumblebee (car?)
new? - Tango Optimus (dino?)
new? - Rockcrawler Bumblebee (from Adventure set?)
old? - Heatwave (race car or firetruck?)
old? - Morbot (race car?)

Wave 20 (wave 3 from 2018)
new? - Optimus "trailer rescan"
old? - Quickshadow
old? - Chase
old - Brushfire
old - Bumblebee Night Raptor
old - Tango Heatwave (dragon)