I'm in the same boat. Although I ordered a bit after you (28th October) I've been sent two return packs as it was an early upgrade. However as my iPhone hasn't arrived I can't return my current phone, I've been told it needs to be returned by the 13th November however that's only 3 days, and it's highly unlikely my iPhone will arrive by then.
I've been told that if you don't trade it in, in my case, I will be charged a fee of £495 which is added to my next EE bill for "non-trade in", the company arranging it all is called Likewize.
It doesn't bother me too much as I can still get just over £400 for my current phone on sites like Music Magpie etc and even more for it on eBay as I have a Mous case (which are expensive) and a few other accessories, so ultimately i'll just pay the £495 fee and get most if not all of that back when I sell the device after the iPhone arrives.
Currently Apple's production is very limited and people are waiting a fair amount of time, I'd estimate that orders will start being received in late November to early December. If you've ordered the same mode (Pro Max), colour and capacity then you will likely receive yours before I do, unless EE receive enough stock to fulfil both our orders.
