I sure hope not, or not without a very significant chance of failure and-or wild surge.
And does that mean armour proficiencies a la 3e are still in? Sigh...I far prefer the simplicity of class x can use up to armour y, as in:
All Warrior classes: any
Clerics: any unless forbidden by deity
Druids: leather, hide, or lighter*; use of any metal armour blocks spellcasting and restricts or cancels other abilities
All Rogue classes, Bards, and Monks: leather or lighter*; use of heavier severely restricts or cancels many class abilities
All Wizard classes: none*; use of any armour severely restricts or blocks spellcasting
* - occasionally, very rare and extremely expensive armour may be found that has been enchanted so as to bypass these restrictions.
Lan-"keep it simple"-efan