Whatever happens you will definitely not need to by any wall charger at all. This contrary to any advice from anywhere at all.
If you are very lucky you will still be able use ALL the USB A charger leads you used on older series Apple Watches.
Mine all stopped working on 8.3 update in December and still does not to this day.
My advice if the old still do not work is to buy USB c female to USB a male adapters from Amazon or EBay for the third of the price of a USB c fast charger.
I say adapters because if you buy one you have just the 1 wall charger to take all over the house instead of Watch and yes the new lead in box.
My findings are that fast charger waste of time anyway. The set up in photo shows original iPhone triangular 5w charger charges from 4% to over 80% in 36 minutes. who needs faster?
This until eventually Apple get the software update that they promised would let us use all our old chargers we did with AW7