@FairyElina : Short answer : in my opinion, the Fire Phoenix is unquestionably superior to the Twilight Phoenix, and if I had not already spent a lot of time, Blueprints, and Spell Fragments buying Artifacts to evolve my own Fire to Stage 10, I would definitely be using the currently available Tomes to obtain original [Fire] Phoenix Artifacts - to the point that if I did not see many (or any) Tomes appearing randomly in my Magic Academy, I would even spend some of my very few and, to me, very valuable Sips of Clarity to cycle through the available recipes in the hope that a Tome would appear.
Longer version : I am by preference a competent (not expert) fighter with reasonable (but again, by no means impressive) Tournament and Spire performance (Halflings Chapter, Tournament average ~3,000, Spire usually two floors weekly with full completion every 4-6 weeks). I would say that the Fire Phoenix is not only one of the best buildings in the game, but arguably
the best fighting-related building bar none. In fact, since the Fire Phoenix was introduced, it's my opinion that the game has been gradually balanced in combat terms to actually assume that most players will own a Fire Phoenix by around the mid-game point, since the advantage of giving all of your Troops +50% Damage Bonus for 24 hours, costing one Pet Food, is obviously enormous. Without activating my Fire Phoenix, and especially in Tournament Provinces above 15-20 [depending on Enemy Troop type combinations] and/or in the third floor of the Spire, I typically lose 30-50% more Troops, and find many more Encounters either entirely unwinnable by combat or at least very costly (i.e. losing 3+ full Squads of my own - and I have a very large Squad Size by design).
By comparison, the Twilight Phoenix is arguably an above-average building for combat-centred players who plan to (or already do) achieve
significantly above-average Tournament and/or Spire performance(s), and it will certainly be useful to expert-level and/or highly competitive fighters (such as our own CrazyWizard - who is probably one of the most successful and high-performing fighters in the game, never mind only on this Forum!), but I don't think that the average or even somewhat above-average combat-focused player will find the Twilight particularly useful, and will undoubtedly find it far less useful than a Fire Phoenix, even at non-full Evolution status.
I have planned my game primarily around fighting, and I've already said that my Squad Size is very large (in order to extend my Troop Training time), so I myself am hoping to be able to place a fully-levelled Twilight Phoenix as well as my Fire Phoenix - but only as a useful addition to the Fire Phoenix. I wouldn't even consider placing the Twilight
instead of the Fire (even if the Fire were at, say, Stage 5).
It may or may not be possible to obtain a Twilight Phoenix in the future, but its effect is so marginal for any player who is not at least above-average in their combat ambitions, whereas the Fire Phoenix's effect is so major for
any player who engages in
any combat at all, that I don't think it's worth worrying about whether or not the Twilight remains an option. It's also true that if/when the Twilight Phoenix reappears in future, it will very probably be obtainable either via Spire prizes and/or via Crafting - but, like anything else in the Spire or in Crafting, it will be on a random basis. I'd mention here that it took me a full year to get enough Artifacts to evolve my Fire Phoenix to Stage 10 - mostly via Crafting, but also by exchanging newer Phoenix Artifacts for the original [Fire] Artifacts whenever I could.
Hope this helps.