This simple dialog from the iOS email app. Spark illustrates how you need to consider different possibilities when creating copy for dialogs. In this dialog, “Please wait a minute” might seem like a great choice, it’s polite and gives what could be an accurate estimation of the task completion. The graphic also gives the user a sense of progress. Unfortunately in this instance there was an error which prevented the process from being completed, turning an estimated 1 minute task into 5 or more. It’s hard to accommodate outliers but it’s how you handle these instances that make a greater impact.
In the absence of accurate data (this I am sure was supposed to be a very short process so they likely decided not to include a progress bar) it’s important to properly set user expectations, well it’s always important to do so. Copy plays a big part in this.