over my head but will the increase in density cause higher temps if we carry on down this road ?

Temps won't be the issue, the issue is like all SSDs in Wear. If you lose a single bit in a 5 bits cell then you lose all 5 bits. So the higher the density the larger the loss when errors start to happen. Prices will be lower but warranties will be way smaller or they will need to have 50% more redundant cells just to cover a 5 year warranty.