Only you know if you’ll own too much. Once the 10Ah 18W Powercore came out, I own three and gifted the older 10Ah 10W to two family members, who used, and still are using, them to get 4+ years of life from the Lithium.
I’ve yet to own any wireless recharged products so I’m not buying any of these 1st or 2nd gen wireless Powercore, the 3rd wireless Powercore version imagined is the one to get.
I’d suggest to feedback to your own words is wait for a 20Ah 20W wireless Powercore as a better / good fit to your needs rather than a buy another 10Ah 18W wireless Powercore? Sufficient community members have asked for 20Ah wireless Powercore I can see the feedback causing such to exist, and not be difficult for Anker therefore earlier than later. It’s simply the electronics of the 10Ah 18W applied to the 20Ah 18W.
A 20Ah should have more place to dissipate wireless heat so should be able to be more W, say 15W?