Should I keep the weapons I get from main quest?

[XoGabrielXo]

Will I even need them to upgrade other things?

It's just taking up a lot of space. I know to keep the mats, but I was just trying to be cautious just in case. 

[MassiveEgo]

Nah, no point in keeping them. Only if you like some of them as skins and they can be used as skins (export available), otherwise just bin everything - you have to sell them to a merchant, you can't destroy them (including the scaleburn weapon but only after you get a legendary one with 6 gem slots).

[Prototypemind]

As mentioned, keep them if you like the skin. Some can never be obtained again if you trash them.