Update: Looks like shipping times have quickly changed back to ‘In Stock’.

We previously noted iPhone 3GS supplies would no longer be refreshed at Apple Stores, and early this morning (around 2:20AM PDT) shipping times at Apple.ca were moved back to 1-3 days for the iPhone 3GS and iPhone 4, corroborating the earlier tip from our sources.

When shipping times are delayed, this is a possible hint of a product refresh coming from Apple. Given the incessant rumours of an imminent iPhone 5 announcement/launch in September/October, it’s only a matter of time before we find out. The iPhone 5 is already being reported to be under production, with manufacturer Foxconn rumoured to be producing 150,000 units per day.