Arcane will never be like that. The point of burning is to burst like mad or "go ham" as some people call it. You evocate it back up because it tanks your Mastery like crazy, and you want that back. We will never be at a point where we will casually hang around 50-80% mana and continue our rotation like normal, because that's a 20-50% loss of your Mastery's benefit (essentially, your mastery is multiplied by 0.5-0.8), and with Mastery being your #1 stat (1.05x through Attunement, AND a bonus to your Mastery through Mage Armor), you won't want that to happen for long.
As far as if burning is even a thing or not, that won't be fully known for sure, though Voltaa on the Mage Beta discussion says that we will have a burn/conserve, which I'm kinda excited to have a comeback of. I'm just not sure because ABl is no longer our big hitter like it used to be in LK/Cata.