I'm sorry for double posting but I really felt this should be its own post and I spent a good chunk of time putting this together. After the April trailer, I made a graphic of the status effects that could be seen. Between the direct, the previews, and a couple months of tweets, I thought it was about time to make an updated version:
Not only are a bunch of 1's statuses returning but we also have a previously X-exclusive status with Decoy (Gray is totally going to have Ghostwalker), and Nullify Healing which was introduced in 2. Target Lock is what 1 called Lock-On and X and 2 called Taunt. I think Power Charge is the same as X's supercharge and 1's magnum charge effect. Damage Link seems to be an entirely new status, I have no idea what it does. I'm also clueless as to what the Arts Pursuit field effect does. For the half-filled heart buff, my guess is it's either Max HP Up, Heal Counter, or Healing Power Up.
The purplish icon with what looks like 1's aura icon does seem to indicate something like an aura. It has points on both the top and the bottom to show 'auras' can have both positive and negative effects. Characters with this icon also have golden energy swirling around them. You can see Mio cast her buff art in multiplayer's preview. It grants her evasion up at the cost of lowering her attacks. Instead of receiving individual evasion up and attack down icons, she gets the purple status icon. It's safe to assume Heavy Guard's Guard Stance art is the same as it gives the caster both a buff and a debuff.
I think some other art effects we've seen that offer something very unique will also be auras rather than having individual icons for those effects. Maximum Voltage makes it so your attacks can't be blocked and we haven't seen an icon for that effect but I have seen characters in the ogre class get the aura icon a few times. Night Hunt's effects also seem unique and specific enough to be an aura. Night Hunt is a non-damaging buff art so the back attack bonus on it is a buff and not saying it deals more damage from behind.
Let me know if I missed something.
Notable statuses from 1 that we haven't seen returning yet: Debuff Immunity, Paralysis, Ether Defense Up, Slow, Bind, Chill, Confusion
Notable X statuses yet to make a return: Slow Arts, Critical Power Up, Debuff Res Down, Timebomb, Control
Notable 2 statuses yet to make a return: Doom