Wait for a 23-inch iMac
Apple could reduce the bezel size of the 21.5-inch iMac to offer up a 23-inch iMac this year.
Apple's offered the 21.5-inch iMac for a long time, and it is a tempting option, but a slightly larger display with an updated design would make more sense in 2020.
The base iMac is $1,099, but if you want an SSD, you need to spend another $200. It would make sense for Apple to offer an SSD with the entry-level model, but there are no definitive rumors yet.
If you want to wait for the 23-inch iMac, you should plan on waiting until the fall, which is the more likely time for this model to arrive.