It is likely that Apple will celebrate the 10 year mark with a redesign like they did with the iPhone X. And clearly it will be the AW X and not just a simple series 10. Or at least that's what everyone likes to believe, I think it's a reasonable assumption. Apple loves their marketing almost as much as money.
I initially assumed the AW X would bring microLED displays as these are much improved from the current LTPO OLED displays. According to rumors though these were never meant for a 2024 release and now rumors suggest that's even pushed back to 2026 and might be exclusive to the AW Ultra regardless.
As the display is the only thing I can really see to be a worthy reason to announce something entirely new and exciting I actually have no idea what they could possibly do with the AW X to make it worth the anniversary. Rumors could be wrong and microLED does come to the AW X despite all suggested delays, or there might not be an anniversary redesign in the first place leaving us with a simple series 10.
You could get a new battery for 100 bucks and sell the AW for about $50 next year, with a working battery and otherwise in good condition it should be worth that much. That way you'll get some money back and you'll have a perfectly functional AW until September 2024.
One alternative is to get the SE 2022 that is currently on sale starting at $189 for the smallest one. So essentially instead of paying $99 for a new battery you pay $90 on top of that to get an entire new AW with a new battery. It's not really that great since it isn't a noticeable upgrade. It's got a faster chip, 2nd gen heart rate (that's not the latest sensor), and in addition to the new battery there's the year of warranty of course. If you have a family member to hand down the AW SE to September 2024 then it wouldn't be a bad idea.