According to the item descriptions nothing would happen if you placed a sac dévorant into a sac sans fond, but if the sac sans fond were placed inside the sac dévorant it would then create a hole to the astral plane.
Not all items are created equally, they all don't share the same weaknesses is basically what I'm trying to say.
The rules are very careful to let you know if an item has a specific interactions with other items/situations, which is why the sac sans fond, trou portable, and havresac malin all have a rule added to them specifically:
Placing a sac sans fond inside an extradimensional space created by a havresac malin, trou portable, or similar item instantly destroys both items and opens a gate to the Astral Plane. The gate originates where the one item was placed inside the other. Any creature within 10 feet of the gate is sucked through it to a random location on the Astral Plane. The gate then closes. The gate is one-way only and can't be reopened.
Other items and spells work like poches profondes, a ritual introduced in "Rituels au Niveau Héroïque" (Dragon #405):
For the duration of the ritual, five pockets or pouches sewn into the garment may each hold 50 pounds of weight or 5 cubic feet of volume (totaling 250 pounds). Items in the pockets do not change the garment's form or weight. Items may be retrieved from these pockets as a minor action. When the ritual ends, items remaining in the pockets appear in a pile at the garment-wearer's feet.
These are missing the additional rule. This makes it logical to assume that if clothing under the effect of a spell like poches profondes was placed in a sac sans fond, nothing would happen, but like the sac dévorant, placing the sac sans fond into the pockets of the clothes would cause the astral hole.