When I have saved and invested around 500k in euros, this will generate about 20k euros per year. My mortgage will be paid as well, so it will be enough to live on. I'll be 55 by then.
Here in the UK inflation was 18% in 1980. It's been over 10% several times since then. 4% assumes things will carry on as they have been for the past couple of decades. There's no reason to believe that.
But if you don't hold too much cash/fixed income securities and actually hold equity investments (e.g. real estate, stocks), then why would inflation be a concern? All those investments should easily keep up with inflation by their very nature, or am I wrong?