The thing is if they let technology advance to much in the same way real technology advanced you are going to end up with a sci-i/fantasy rather than just a fantasy.
People are right to use star wars as a comparison it is both sci-fi and fantasy obviously it is more sci-fi and most people would call it sci-fi but it has some fantasy aspects.
I hate having to say it over, and over but I will. Redguards+cannons=potential to make guns within 200 years.
You assume that technology in Tamriel will advance the same way as technology in the real world did even though we can clearly see it hasn't so far because it is a different world a fantasy world. It can be as simmilar or as different to this world as Bethesda want it to be. Maybe in Tamriel nobody will ever invent a gun or maybe such a thing is simply impossible in Tamriel Who knows?
The thing about guns is that they are too much like the world we live in they don't fit in a fantasy world at all well. games with guns in have to completely change what we know guns to be capable of