One general change of powerleveling we will all be feeling, along with every other manatousing class, is the Replenishment nerf or mp5 buff about powerleveling. Overall, we will be losing mana, and though the loss is not steep, trust me when I tell you that you will notice. You can find the details here.
Mana cost reduced by 12% about Maple Story mesos. Invisibility: Can no longer be interrupted by a hostile action or damage done during the 3 second fade time, however an invisible mage can still be stunned or silenced to get cheap Mesos. Mirror Image: Images will no longer trigger the death sound when their time expires. Not much here, really. The major change is the Invisibility one to get Maple mesos. I think we can all agree we are looking forward to not having our escape mechanism or aggrotodump interrupted by a stray AoE before it is done us any good. The Arcane Blast mana cost reduction is a pretty clear maketoup call to help the replenishment nerf sting a bit less, and the Mirror Image change will be a pleasant cosmetic change.