If yes, will Dogmeat have some kind of inventory to carry loot?

I would assume he does, he is refered as a companion by Beth.

As for inventory, well there was a rad option when you talk with him *shrugs*

You can "Trade" with him, so I assume he can carry things for you. It would be cool if you could find like an old K-9 vest for him to wear.

I'd say of course he does, he's a companion after all. Also, in past games nonhuman companions could carry items so the assumption is that you stuff the items up its doggy derrière.

But dogs don't have pockets.. Think about where you will be sticking that loot into... that poor, poor doggy. If my doggy isn't wearing some sort of pouch I'm certainly not going to be using him for storage.

Well, considering that Mad Max Rockatansky, THE lone wanderer, has a dog, I would hope not.

Damn it is going to be a hard job putting that mini nuke in his "storage space"

Not to mention the Fat Man after that.

Really hoping he does not count as a companion for that perk

Whilst I understand Bethesda calls him a companion I hope he doesn't count as one for Lone Wanderer. I want to feel that self-reliance and isolation (from civilisation) in the wasteland but at the same time have something to share it with, if you know what I mean.

I'm pretty sure Dogmeat counts as, if I understood, as a "companion", as you can only have companion, no matter of "species" (unlike Fo3 and FO:NV where you can have a dog and a human(oid)). Hope not, but I would not be surprised either.

For like 5 seconds in one out of four movies.

Well I certainly hope not, the added carry weight perk would balance between dogmeat and the pack mule followers.

It is all about balance.