Apple’s a company known for surprises, but their catalogue is refreshed on regular schedules. There’s a new iPhone every year. MacBooks tend to be refreshed twice a year, every spring and fall. But desktop models are refreshed less frequently, usually once a year.
This page shows where each model sits in its refresh cycle. Is the current iMac coming to the end of its cycle? If the bar is to the far right, then yes it is, and you probably should hold off buying it. Wait until the new model is released (or you can pick up the old model at a steep discount).
Be warned: this information isn’t written in stone. The data is based on past upgrades and release cycles. We’re just trying to provide our best guesses about Apple’s release schedules. We provide no guarantee to the accuracy of this information, and take no responsibility for purchase decisions made based on it.