One of the things I liked about 3.5 was the need to use certain types of weapons and materials to overcome DR, or be so strong you powered through.
In PFRPG Beta page 394, there is an allowance for high-bonus magic items to overcome this on sheer magic power: "Overcoming DR"
This makes it silly to have a cold iron or silver weapon higher than +2.
There are also no mentions of other possible special materials or weapon shapes this applies to.
Does +5 weapon negate the need for crushing or slashing?
I would rather see the last paragraph and following table dropped, my group is doing this already.
One other thing we do allow is for mithral weapons to count as silver for the purposes of overcoming DR.
Bonuses of +3, +4, or +5 have many other broad benefits: increase to hit chance, increased damage, increased ability to perform maneuvers, etc.
There is no need to gild this lily.