The "immediately" online behaviour isn't really immediate, you will typically have been disconnected from the AP. In fact, this disconnection is now going to be enforced for 3.10 because the other behaviour doesn't gain a whole lot (you still need to reconnect etc.) and trying to keep the connection causes a huge amount of issues, particularly with USB hardware (that can be unplugged while suspended.)
However, a much easier solution could be implemented in NetworkManager: instead of scanning on all channels when resuming, it could scan just the channel that it was previously connected on. If that finds the previously connected AP, it would be able to reconnect almost immediately (delay of less than half a second), vs. a full scan that can take up to 10-15 seconds. This should be a fairly simple NetworkManager change.