No simple answer. It is a function of both location & price range. Good locations are likely to decline some what less while the bottom will fall out of the lowest fifth or so (in desirability).
In terms of price, the Jumbo kind in the 500K – 800K will get hit hardest. Practically that market has gone away overnight due to near non-availability of reasonable mortgage.
If you integrate all transaction over next 5 years, my guess is a 50% decline in today’s prices. Of course, if inflation is severe, the nominal decline may be much less. In case of hyper inflation, there may not even be a nominal decline (or may be there will be a net increase, nominally). If that happens, you can of course see the impact on exchange value of $ and also purchasing power decline.