Kegging a weissbeer

I am about to keg a Weissbeer that I brewed. Looking at various references, I chose 4 volumes of CO2 for forced carbonation. At a kegerator temp of 38 F, Brewer's Friend tells me the keg pressure should be at about 27 psi. OK, so I leave it at that pressure for a week or two to carbonate the beer. My question involves dispensing the beer after that. Would I drop the pressure to the normal dispensing pressure of 10 - 12 psi? If so, does that not mean that, over time, carbonation in the beer would go down as there is less pressure in the head space? I mean, the same PSI calculator shows that at 38F and 10 psi, only 2.4 volumes of CO2 would be in the beer. Would my weissbeer go down to that 2.4 volumes of CO2 eventually?

Would appreciate your sharing your wisdom and experience.

You're intuition is correct. At your dispense pressure, the keg would slowly decarbonate until it matches the head pressure.

Another consideration is that you'll get foaming unless your draft system resistance matches the beer's carbonation. Since it's unlikely that you'll add a bunch of tubing or a choke into your draft line, you should consider just carbonating to 2.4 volumes.