When I run my app in the iOS Simulator using 2016r3 and Xcode 8.1, I receive the following message:
“Myapp.debug” May Slow Down Your iPad
The developer of this app needs to update it to improve its compatibility
Is a Xojo update required?
As I think to remember that message appears if you’re running a 32Bit app on iOS 10.
And that’s most likely the case while Debug-Running from Xojo.
Yes and no 
Once 64Bit Debugging is available in Xojo you won’t get that message any longer.
As long as Debugging is 32Bit you’ll see the message - and you can ignore it.
The message won’t appear in a Xojo-built (64Bit) app.
Just don’t forget to test your Xojo-built (64Bit) app on a real device as well…
If I am not mistaken, 2016r3 only produces 64bit iOS apps (for both release and debug). So it must be something else.
No, he’s correct.
Does anyone know when 64 bit debugging will be available in Xojo ?
For macOS and Windows, this is planned for this year (according Xojo Inc). Not sure about iOS though.
It should be there in 2017r1 for the simulator.