Remember, Apotheker stated, several times that this is not a sprint, but a marathon - they are in it for the long haul - I'd expect to see lots of things happen over the next few years to continue building on their mobile initiative, which is built completely around WebOS.
As for the old failure of the Pre - its true, there was the iPhone, and nothing else, and the Pre was dubbed by the press as the "iPhone killer", and it fell short, leaving a gaping hole for android based smartphones to fill that gap.
Now, 2+ years later, we are looking at a playing field with hundreds of different smartphones out, and may people have already changed devices 2 - 3 times.. having said that, the Pre3 will perhaps not stand out as an evangelical device, but, will certainly garner some good attention, and if its a decent phone, built well, performs smooth and is supported well, at the very least, it will be a well respected device with a decent following.
People will switch to try something new.. many people really want a portrait hardware keyboard still - and this could be enough to get them to try it.
We'll see how things unfold, but, I believe HP will be a strong advocate of their market entries, in a building fashion of intensity over the next few years, as they find the direction the market takes them in.