My personal prediction taking into account some recent rumors...
Base iPad 2020 (released in fall)
A12
Laminated, antireflective, but otherwise the same 10.2 display with bezels and physical home button, without true tone and P3 (or mayyybe the 10.5 display from ipad air 2019, but I think that might be a stretch due to price)
No 5G
Same cameras as 2019 (or at maximum slightly better selfie camera with 5-7mp)
Exact same body as 2019
Same Touch ID in home button
Same WiFi 5 and BT 4.2
Same 3GB RAM
Lightning
Starts at 32GB with the same pricing
iPad Air 2020 (released in fall)
A12 or A13 (more likely A12, because ipad pro 2020 has A12Z and A12 has still enough power. A13 only if they want to more distinguish Air 2020 from base iPad 2020, but I think it will be different enough due to upgraded body and display, which also cost more, so a saving needs to be done somewhere + base iPad had A10 for 2 generations)
WiFi 6 and 30 band LTE (same as ipad pro 2020)
All screen display similar to ipad pro 11, but possibly smaller screen, like 10.8 = slightly bigger bezels
Body recycled from ipad pro 11 (compatible with expensive magic keyboard, apple pencil 2 = more revenue)
4GB RAM (to compensate for more pixels and distinguish from base ipad 2020 and ipad air 2019)
Face ID (because it is not a pro feature anymore, think iphone xr, iphone 11 and because it is getting cheaper)
USB-C
No 5G (more expensive and not mainstream, will be introduced in iphone 12 and then ipad pro 2021)
No promotion (pro feature)
No mini-led (will be introduced in ipad pro 2021)
No lidar (pro feature)
Just one rear camera (pro feature, because unlike iphone xr/11, mainstream ipads are not used for photo shooting as much)
Starts at 64GB with the same pricing (more base storage = pro, mainstream users don't need as much base storage, this keeps starting price down, compensating for the new body and display and face id)
iPad Pro 2021 (March or WWDC 2021)
A14X
5G
Mini-led
Better/more cameras
etc..
iPad Mini 2021 (March or WWDC 2021)
Same as iPad air 2020, only smaller, so requires more time to develop before release.