Can legendary weapons combat rating be upgraded higher?

[Yaltiaj]

I have a gun and a melee with a good roll that I really enjoy, but the combat rating is lower than the newer gear I'm finding. Can I upgrade them higher, or is throwing them away the only option?

[RNG]

It seems to be that- an absolute GOD ROLL legendary would be at maximum 550 or 560 power.

The only way to get a high power level legendary is one of two: Get lucky via mission drop or find a White Weapon VIA the shop, that is at least 340-350 power level.

Upgrade that white weapon to legendary and you will BE SUPER LUCKY if it is over 500.

[Dragon]

So right now from what I've gathered

400 is the theoretical max stats roll for the weapon stats themselves
+50 from top rolled perks
+~100 from top tier/weapon specific blessings.

If it allows 100% at any point in the future, that would just add 100 to the base rating of the weapon, giving us a theoretical max of ~550-~650

[Dragon]

However, since none of the crafting system outside of upgrading and praying is in the game, we will never know