Right now, we can only guess at this. I'm hoping that the new engine will be better optimized than Oblivion, and load more quickly, but I won't get my hopes up too high. I could see the loading times being similar to Oblivion, or possibly worse, due to having more data that needs to be proccessed as a result of the technical improvements, but like I said, it will depend a lot on how well programmed the engine is, I've seen games that look better than Oblivion but load quicker (Of course, the large amounts of mods I'm using with Oblivion, some of them likely fairly resource intensive, probably don't help to cut down on my loading times anyway.) but like I said, it probablty depends on the engine.
Of course, I don't know how loading times were on the PS3 and Xbox 360 anyway, but I'll take your word for it that they were bad. As for the PC version, obviously, it's going to depend a lot on the user's system, though even on the same hardware, the loading times might be different from Oblivion's as well.
Yes, we can. No matter how efficient your software is, there is a physical limit to how fast you can read data from a specific disk. You simply cannot load large amounts of data from a slow medium quickly, there's just no way around that.
Then I think the important question is, how much of the loading times Oblivion players experienced on consoles came from the software optimization and how much from the limitations of the hardware? And that's a question I don't know the answer to.