If the Errata team decides to go with 5th edition style burn out rules the character is still legal. Max Magic never hits 0.
If the Errata team decides that Power Points can go negative, the character loses the one Adept Power. Never happened in any other edition though.
If the Errata team decides to re-define Max Magic in some way, the character could become a total burn out.
If the Errata team decides to define Burn out as Magic (not Max Magic) as 0, then the character would burn out. Similar to editions 1 through 4.
If the Errata team decides to define a specific order of operations for character generation, then the character could burn-out or lose the Adept Power in some way. But the order of Magic --> Install 'ware --> Increase Magic has always been left to the player's benefit.
The Errata team could come up with something completely novel regarding burn-outs that I have no way of foreseeing.
If the burn out rules from 5th are copy/pasted into 6th, the character is legal and that seems as safe a bet as any, while remaining 6th edition rules legal as well.
Way too hard for me to guess what the rules will be after the Errata and Mission FAQs are completed, unfortunately. And as you pointed out, it could be a long time before the Errata gets approved and released. Burn-outs could have their own source book by then. Or at least their own path

(again).
If char gen rules get Errata'd then people will have to re-make characters. Hopefully the Errata team is sensitive to that.