Thanks, all, for your very helpful replies. We do use mesh WiFi-- there is an Orbi satellite bout 15 feet above the pool equipment that serves that side of the house, so I was thinking WiFi range wouldn't be a problem. I'll do some searching about whether this might be a problem, but it seems like worst case, I could attach a cheap WiFi router to one of the ethernet ports on the Orbi with some distance just to serve the IQ-20 if there's a problem. The Orbis (base+2 satellites) have made a huge difference in our house.
The bid does specifically say
IQ20 RS I-AQUALINK UPGRADE KIT and I'll confirm that.
We don't have the PDA -- have talked about that upgrade at various times the years, but phone/web integration always seemed on the horizon, we've also been talking variable speed pumps at the same time and those would have entailed an intermediate upgrade at the time (we're at NNN). Glad we waited. We currently use the OneTouch panel inside for programming and have a Spalink to turn things on and off from outside. Sounds like if the OneTouch will keep working, there's no reason to remove it from the wall, as it'll be a backup.
This all sounds ideal and exactly what I'm looking for. I'm sold. Just hope they can get the parts.