I've already replied to the post before stating my updates, but I'm not sure everyone has seen it. As a recap, I purchased my Elite 2 controller on April 17th. The original arrival date was said to be between April 21st-23rd. I contacted customer support on April 20th, and they stated that the item is on backorder and will now arrive on May 6th. Just to check on any potential progress, I contacted customer support again on April 23rd for another update. They stated that May 6th is still the ETA.
To add, my order has been pending this whole time. Being that the item is back-ordered and from the feedback on this thread, you will most likely not see a change to this order status until the item has already arrived.
Essentially you have two options, wait for your controller for approximately 2-3 weeks from the original arrival date or cancel and try to find one at another retailer. My opinion is just waiting. I've tried to find this controller at other online retailers and along with the ease of any potential warranty claims buying directly from Microsoft, I couldn't find it anywhere else without it being back ordered or marked up 20%-50%.