Yea, it would be a refreshing change to be surprised by a Regeneration.
I watched Classic Who on PBS, before this new fangled Internet thing, and didn't know a thing about what was coming in the next episode (Or even when new episodes would stop). So, every episode (That was new to me) was a surprise. I remember the 3 Doctors, The 5 Doctors and The 2 Doctors all were a surprise to be multi-Doctor Specials as were all the Regenerations). Even having seen the first Tom Baker, Pertwee's Rgeneration came as a surprise, since Pertwee hadn't been shown for the first time until after Baker had aired several times, and Davison had aired. Likewise, having seen Pertwee's first, Troughton's Regeneration came as a Surprise.
Yes. But if you had been living in the UK at the time those episodes were about to air, you would've known about the impending regeneration. Because you were living in the US, pre-internet, you weren't a part of the PR experience. You got to have a thrilling experience because of it, but, it was unique to where you were living--not to lack of PR on the BBCs part.
I get the desire. And a part of it is watching a show take an actual risk. But, I don't think it would happen. The bigger a franchise is, the more risk adverse they become.