The demo for these new skills will be available on for one weekend, August 18-20. According to a recent Developer Diary:
The developers have expressed that they wish to create new avenues of play for the existing classes – and in doing so, they have given a new life to an old profession. For example, the new Holosmith elite specialization will provide the Engineer class with a second melee class. Holosmiths will be equipped with swords and a Photon Forge mode that generates heat with the use of abilities. This heat will damage the player, but will also increase the effectiveness of utility skills. This addition takes what once was a ranged crowd control class, and turns it into a viable melee damage dealer.
If you wish to see the Elite Specializations in action, head on over to the Guild Wars 2 Developer Diary, where ArenaNet has posted demos videos of each new Elite Specialization.
Will you be trying out these specializations during the demo weekend? Which one are you most looking forward to trying out? Let me know down in the comments!