The ArenaNet team is calling this new chapter "Strikes 2.0" and there will be new challenge modes in this new chapter. So there will be an opportunity for those that want a little more of everything in their Strike Missions to be put to the test. With this, there will be differences in the difficulty ramps to consider and the whole thing should feel like a properly challenging raid boss.
While each Strike Mission is initially designed to a specific standard of difficulty and playability, this time around, with Normal and Story Mode, they've been tweaking those designs in order to focus on things like the skills and abilities needed to learn and develop in order to succeed. Challenge Mode, long requested as a feature, will be built first and not just be boosted to up the ante based on the work they've done for Normal and Story modes. Challenge Mode, with all its elements, timing, skills, damage, and mechanics are all built first and pared down in steps. In other words, the hardest difficulty was done first and then analyzed for how to make it easier to complete. With the new options, Strike Missions let everyone have an experience at the level that best suits them.
Another change is the overhaul of the rewards systems. Instead of divided rewards and currencies, they'll award just one currency and the whole thing won't be subject to the weekly cycle restrictions. Further, they'll consolidate Icebrood currencies into one as well, and End of Dragons Strike Missions' currency will be tradeable for those rewards as well.
Challenge Modes won't be in at launch, but will follow in the weeks afterward, to allow for new story play, and, of course, adjusting to the whole slate of new Elite Specializations.
For more, see the full post on the Guild Wars 2 site.