We are also about to build our house and 8 months ago we still had an offer with 2.8% over 25 years and today we are at 2.01% effective over 25 years. Waiting really paid off! The amount was 280,000 euros! Of course, there are still interest rates under 2% but I don't trust that. After 10 years the interest rates will certainly be higher than now and then you are left with a considerable amount.
That you can see how the interest rate development was in our case. That 8 months brought us an additional plus of 0.8. Sorry that I wrote something, I wanted to add... really surprising what kind of people you meet in this world.
With us, the interest rate development went in the other direction.. we got 2.35% and then it went back up to 2.9%. Well, and since then steadily down. But as others have already said, nobody can see the future. It’s all speculation!