?
Sadly there are 3 options, not 2.
1. It never arrives.
2. It does arrive.
3. Contact TfL now.
IMO, 2 and 3 are linked.
Can't recommend 1 because it's speculative and high risk.
If it arrives late, you won't be able to prove as such and as the 14-day extended discount would probably have expired (arrives later than 27th because TfL's website says your reps rejected on 13th) then you'd have no choice but to appeal with the full penalty in play.
I don't understand waiting(hoping?)it won't arrive because all this would do would be to cause you to engage with the OfR process which at best would lead to TfL sending you a copy of the NOR and probably extending the discount whereas if you engage with TfL now and explain then if they sent a copy today you'd at least have 4 days to review their NOR. (
https://tfl.gov.uk/modes/driving/red-routes/penalty-charge-notices/enforcement-process)
NB. if you phone them and receive any verbal commitments then you MUST confirm in writing by email. Never take verbal assurances.
If you can't contact them today then the decision to wait is made for you until next week at least.