If this is true, then it will be a dent in the feeling of immersion of the game. Actually they could do a 24 le mans only by day, GT 4 did it, but that was last gen, and there have been a lot of racing games that have since then incorporated night/day cycles and dynamic weather changes.
Hopefully they can mend it by the time of release, but I don't think that this will deter most of the Forza fans that are waiting for this game.
To me, personally, is just another reason to buy GT 5, not that i'm against Forza, i've got Forza 2 and enjoyed it, but GT feels like a better sim to me.
Current PC Build
CPU - i7 8700K 3.7 GHz (4.7 GHz turbo) 6 cores OC'd to 5.2 GHz with Watercooling (Hydro Series H110i) | MB - Gigabyte Z370 HD3P ATX | Gigabyte GTX 1080ti Gaming OC BLACK 11G (1657 MHz Boost Core / 11010 MHz Memory) | RAM - Corsair DIMM 32GB DDR4, 2400 MHz | PSU - Corsair CX650M (80+ Bronze) 650W | Audio - Asus Essence STX II 7.1 | Monitor - Samsung U28E590D 4K UHD, Freesync, 1 ms, 60 Hz, 28"
