Disney Answer: Yes!
For many years, you could not walk from the Grand Floridian to the Magic Kingdom. Even though the two are only several hundred feet apart, Disney made it impossible to walk between them. There is no path or sidewalk, and the two are separated by a fairly large canal that connects Seven Seas Lagoon to the Rivers of America inside the Magic Kingdom (it is also used for the parking area of the nightly Electrical Water Pageant floats).
Curiously, on the Contemporary side, there has been a walkway since the resort opened.
However, as of early 2021, there is now a completed walkway from the Grand Floridain to the Magic Kingdom. It is a long walk, but you get fantastic views of both the Contemporary and Grand Floridian as well as the Seven Seas Lagoon and the monorail.
The good news is that the resort monorail continues to stop at the Grand Floridian every few minutes and goes directly to the Magic Kingdom monorail station, and requires way less walking.
How long is the Walk?
@Danielle – Once you are out in front of the Grand Floridian, the walk takes me about 10 minutes to the entrance of the Magic Kindom. I walk pretty quickly though, so my guess is that for most people it is a good 15 minute walk.