No, they are not becoming CE-legal.
But, for those of you who wish to play with them in any format (casual, Draft, Open, Legacy, Multiplayer, etc.), I have good news!
Effective immediately, all 109 non-CE-legal Flashback cards have been issued errata updating them to current wording/templating for complete compatibility with CE cards and Rules (with 3 exceptions).
1. Cards focused for Personalities with the "Double Chi" keyword have their values added twice when determining the duel's winner.
2. "Yoritomo's Alliance" is equivalent to "Mantis Clan".
3. Some cards have the "Unaligned" keyword and/or keywords that mark them as members of non-CE-legal Factions. How these keywords interact with other cards in your game depend on the Ruleset/Format/card pool you are using. But, for strict CE Rules, cards with only these and no other Clan keywords have no Clan alignment, and their labelling as "Unaligned" is redundant with that term's definition.
Flashback Dynasty Errata
Flashback Fate Errata
Below are highlights of significant changes:
General: Implied targeting and performing has mostly been exchanged for explicit targeting and/or performing. Most "Open" actions have become "Battle/Open", being that prior to SE, most "Open" actions were usable in the Action Phase AND Combat Segments. A number of Personalities gained "Toturi's Army" per their MRPs; of note if wishing to attach The Twelve Ronin.
Akodo Toturi: Is now titled "Toturi", will not be controlled by Scorpion Clan players in additon to Crab and Phoenix, and his Force bonus due to rehonoring is now a Reaction. (Per OE MRP)
Another Time: Is now a Focus Effect, not a Reaction. (Conformed to new duel mechanics)
Bayushi Kaukatsu: Has "Courtier" instead of "Diplomat". (Per DE MRP)
Bayushi Saya: Her delayed effect triggers upon the Personality's controller assigning his unit, not anyone assigning it. (Per SE MRP)
Brothers in Arms: GC is 3 not 4, fetching another is a Reaction not a Trait. (Per SE MRP)
Crushing Attack: Explicitly requires the presence of at least one unit in the enemy army. (Per rulings)
Evil Portents: Bonus only applies to Personalities and Followers, not "cards". (Per OE MRP)
Fall On Your Knees: Explicitly negates, does not "cancel". (Per decision to make terms equivalent)
For the Empire: FV is 3 not 4, and circumstances of both Personalities being Samurai and Shadowlands are dealt with. (Per DE MRP and rulings)
Hida Kisada: HR is 6 not 10, GC is 16 not 14, and his unit is only untargetable by Shugenja/Spell effects, not totally immune. (Per OE MRP)
Hida Yakamo (Oni): Clarifies that it is a distinct card from non-Oni Yakamo. (Per Rulings)
I Give You My Name: Explicitly allows the performing Shugenja to also act as the destroyed performer. (Per ruling)
Isawa Tadaka: Has the "Elemental Master" keyword. (Clarification of "Master of X")
Isawa Tsuke: Has the "Elemental Master" keyword. (Clarification of "Master of X")
Kan'ok'ticheck: Has "Nonhuman" instead of "Creature". (Per decision to make the terms equivalent)
Kharmic Strike: Is now a Focus Effect. (Conformed to new duel mechanics)
Kolat Assassin: Destroys a Personality with Chi of 4 or less, not less than 4. (Per DE MRP)
Kuni Yori (Experienced): Is not Crab Clan. (Per PE MRP)
Moto Akikazu: Does not have a Chi penalty in duels. (Per SE MRP)
Moto Chagatai: Trait is explicitly negation. (Per contemporary Rules)
Naga Abomination: Is Unique. (Per OE MRP)
Night Medallion: Now explicitly gives bonuses to stats and Ranged Attack strengths. (Per rulings)
Ninja Spy: HR is "-" not 0. (Per GE MRP)
Secrets on the Wind: Performing Scorpion Clan Shugenja need not pay the cost of destroying a token. (Per GE MRP)
Shame: Is "Political" and cannot be played on the same Personality unless he becomes rehonored and is dishonored again. (Per DE MRP)
Shinsei's Crow: Has the "Nonhuman" keyword. (Logic)
Shinsei's Shrine: Is "Singular". (Per DE MRP)
Tamago: Has a new trait preventing Tamago (Experienced 2) from overlaying him, because they are not the same character. (Story)
The Egg of P'an Ku: Is a Strategy, not an Item. (Per DE MRP)
Togashi Mitsu: Is also a Monk. (Per PE MRP)
Togashi Yokuni: Ability is "Any number of times per turn". (Per intent and contemporary Rules)
Tsuruchi: Is "Yoritomo's Alliance" and "Wasp Clan" instead of "Unaligned". (Per PE MRP)
Void Dragon: Force is 6 not 7, GC is 14 not 11, discard effect is now a Trait not a Reaction, and has "Nonhuman" instead of "Creature". (Per DE MRP and decision to make terms equivalent)
Wandering Budoka: Has the "Budoka" keyword. (Logic)
Yogo Junzo: His ability is extrapolated from old Fear ability Rules.
Yoritomo Utemaro: Ability is "Any number of times per turn". (Per intent and contemporary Rules)