The next 24 months will be the worst segment of the housing downturn. As the 2nd and 3rd (or 3rd and 4th, depending how you measure) year of the slowdown, this is typically where prices accelerate to the downside.
I expect a drop in median SFR Central SD of 5-10% each of the next two years. I’d guesstimate ~15% over the next 24-30 months in the median, putting the total drop in median somewhere around 20% from the peak within 2-2.5 years.
That said, individual homes will likely experience more significant declines. But you asked about the median.