Maybe you could, but I doubt you'd see much, you could see into parts of other provinces in Oblivion too, but it would just be trees, rocks and other generic terrain features, I wouldn't be surprised if Skyrim is about the same in this regard.
So you'd rather explore said place populated by only land and trees and find what's supposed to be a densly populated province is actually an empty wilderness without a single interesting thing to see and eventually just drops into an endless void or whatever it is that happens once you reach the end of the terrain Bethesda modeled? I for one would find that MUCH more "immersion" breaking than invisible barriers I'll only notice 0.000000001% of the time I spend playing the game (Seeing as I'm not usually in the habit of trying to leave the province when I know the game doesn't allow it. Why would I want to anyway if there isn't a single interesting thinmg to see or do there?) not to mention it might lead to me wasting my time as without checking the map, I might not realize I'm leaving the province and could wander for an extended period of time even though doing so is entirely pointless. Now, usually wandering is fine in an open world game, but only when there's actually a chance that something worthwhile can come of it, wandering outside the game's borders, if it were possible, would be utterly pointless as there would be nothing to see or do out there.
I'm perfectly, 100% fine with invisible barriers as long as they're kept only on the borders of the map (Now using invisible barriers to keep me from using any paths to get to a place other than the one intended as in New Vegas, on the other hand, is a big no, if you want to force me down a linear path in your open world game, then at least do it with barriers I could actually believe would prevent me from going off the intended path.). Of course, if Bethesda can come up with a better way, that's fine with me too, but there's not exactly that much they can do, they can't do an endless ocean like Morrowind as it's not an island, and surrounding the entire province with impassable mountains tends to look artificial, like some god put those mountains there merely to keep people from leaving and entering the province, and makes one wonder how it was ever possible for anyone to enter or leave in the first place.
Well it would take you a while to reach the drop off point, I had a mod in Oblivion that turned off the borders, I didn't really explore the other provinces but it just let me explore parts of Cyrodiil that were usually blocked off (since the border wasn't that accurate).Someone suggested incredibly tall mountains that are impossible to climb to stop the player from going into the other provinces, this would be a lot more immersive than an invisible wall with an attitude, and it makes sense because Skyrim is a very mountainous region.