Hi @Tom_Simon, welcome to the Asana Community Forum 
Thanks for reaching out! I’ve tested this on our side and can confirm that selecting “Mark Task for: Today, Upcoming or Later” will still move the task to the selected section as expected on Android!
You are correct in saying that the auto-promotion of tasks is currently being redesigned however, with the new My Tasks, you will be able to create rules to replicate the magic of the auto-promotion for Today/Upcoming/Later sections 
I hope this helps!