I did a bit of reading last night and found out that the new $20 notes were announced at the same time as the $10 notes, but, where the $10 notes went into circulation in late May, the $20 notes weren't supposed to go into circulation until June. This time delay is probably why the $10 notes are starting to hit eBay but the $20s aren't - yet. I figure, assuming they aren't delayed, we'll see the $20s for sale to US collectors by early July.

I said in my post about the new $10 notes that there seemed to be some clear attempts to call back to the original $10 notes from 1980 but it's even more clear with these new 20s

While the design is clearly different, the color choices are very similar with greens, blues, and teals / aqua. Then you get to the art on the back. Both notes have an elephant - or the front half of an elephant - and Victoria Falls. Yes, they've clearly updated the art, but the inspiration drawn from the older note is very clear.