Is there....

[Beryl]

...a dragonling pet like what I see following the ancients around but, instead, a fully formed (and enflamed) Phoenix?

Yes, I've seen the shoulder phoenix in the listings, but I can't find a shot of what it looks like in-game.

(I'd still want the one I'm asking for even if it turns out the shoulder phoenix is other than that.)

I'm kind of a phoenix nut, so anything "phoenix" (Other than Arizona, thanks) I'm usually on like white on rice.

Or I suppose white on Beryl, now that I think about it.

[vasteel]

maybe one day will be available phoenix pet,this not sounds like something impossible for make.

[xWaterwingx]

No, currently there is no phoenix pet. If you've seen the Treat Shoulder Pets, they're the exact same as the Phoenix Shoulder pet. You equip them in the chest slot, and they appear on the character's shoulder.