I was pretty much just speculating out loud. A gun of Sload origins would be great, we need a race that is at least somewhat as focused on technology as the Dwemer were.
Maybe the Dwemer DID make a gun: we just haven't found it, as they were just developing them when they disappeared. Perhaps Yagrum Bagarn, the last Dwemer, returns for TESV and helps us with this? It'd be nice to give the ol' dude a graphical face-lift and put him in the new game, say, by arrival from a boat or something. You give him a broken, gun-looking thing of obviously Dwemer origin, and he fixes it up for you, but doesn't know just exactly what it's supposed to do. Obviously it's supposed to shoot projectiles, but the means through which remain a mystery to him. Then, an alchemist can get involved to make the explosive propellant that the firearm uses, and you can do fetch quests for him. Eventually, he and Yagrum work together to make some ammunition, which you can then buy from the alchemist. TA-DA! I don't know much lore: does that conflict with anything else we know, ANYWHERE?
I've always found the magic argument to be interesting. On the one hand, in OB you could easily learn many... competent spells without a chance of failure. In MW, there was a chance of failure for the spells. Depending on what magic system happens in TESV, we could have different perspectives on magic. Given the unstable conditions of the Empire without an Emporor, perhaps opportunistic warlords will arise. If this is true, they need to build great armies quickly. Swords take some time to master to a degree of competence. Bows actually similarly require training, especially the armor piercing longbow. If magic is OB easy, then the failure rate isn't an inhibition. A hundred people casting 'fireball' is four times as powerful as the greatest spell available in OB. In MW, there's a chance of failure that's significant for young apprentices of magic. A peasant rebellion will get nowhere with an army of unarmed men muttering under their collective breath and wandering around.
Guns could fill a niche that's only recently become existent in such a fashion.