A few months back, I sprained and fractured the thumb on my writing hand. It was almost a week before by thumb was strong enough to even allow me to grip an empty soda can without dropping it, so you can imagine it took awhile before I could write again (nearly two months before I could write more than a few lines, in fact). I also work at a software development shop where a key part of our culture is our use of notebooks. To say the least, I was a bit concerned, since writing seemed like an essential skill.
Because writing by hand was out for me, I turned to taking notes on my iPhone, simply out of necessity. I write by hand at around 30 wpm, I'd guess, which I was able to get on par with almost immediately, without any of the annoying hand cramping that happens after awhile when writing on paper. Plus, the notes are much more legible (even with the occasional auto-correct mishap), have the ability to be searched more easily later, can be synced to other locations, and are "written" using an object I'm keeping with me all of the time anyway. I'm actually seriously considering ditching notebooks altogether at this point, now that my thumb is mostly healed, since I can type just as fast, and if someone throws up a picture on a whiteboard, I can snap a photo more easily than I can copy it to paper anyway.
Which is to say, I'm not convinced that writing by hand remains an essential skill, or else that it will be one for much longer. Useful in numerous situations? Absolutely. Something I'd teach my kids? Without a doubt. But essential? Other than legal and old-world business forms that haven't moved online yet, I can't remember the last time that I had to write by hand, and those are both a dying breed.
Personal note: Just to put it out there, I'm not someone with years of experience as a prolific typist on phones. I'm averse to text messaging and get frustrated when trying to type out e-mails since I'm still, of course, much faster on a full keyboard.