https://www.interhyp.de/ratgeber/was-muss-ich-wissen/zinsen/...
The incredible increase in house prices tracks a dramatic decline in interest rates. Interest rates were at 1% last year, below inflation! I have no idea how interest rates will change in the next few years, but I do know they will not decline at the same rate as over the past 10 years. As soon as they go up, the prices will decline.
Things will be different on the far future. The exact point when it will change is a matter of speculation, and all the warnings about timing the market apply. You implied a high certainty that nothing will change, ever, and talked about 15 years things.
There is a high likelihood that nothing will change in 5 years (even though COVID19 reduces those odds a lot, because a bunch of people just died). And there is very high likelihood that things will change a lot in 40 years. Time things at your own risk.
I'm not looking at any undetermined future point in time, if I'm ranting about housing prices it might be not unrealistic that I'd like to buy one in the next few years - and I've seen absolutely zero indication that the prices would suddenly drop by 20-40% to the point where I'd call them reasonable, like 15 years ago.