First, do you want him to return? (Check all boxes that apply)
YESSSSSsssssSSSSS! I miss him so! My heart seizes with joy at the mere thought of seeing his face again!
Sure, he was an interesting character and I wouldn't mind seeing him back.
No, I dislike manga-ka pandering to please fans of a popular character.
No, I'm an Ulquiorra fan and I think his death was perfect and his story finished.
It's Kubo's choice--if he entertains me with a return scene, I'm all for it, but if he blows the plot and ruins Ulqui's character, I'm against it.
I'll stop reading Bleach if Ulquiorra returns.
There will be no limit to the Schadenfreude in fandom and I hope Ulqui returns to throw Lanza del ReLampago into the throats of his Hatorz.
No, because Ulquiorra has no good reason STORY-WISE to come back.
No, because I don't want him and Orihime to have another chance to noodle fingers together or share hearts or whatever fanservices shippers of that pair.
Other (explain in comments)
Second, do you actually BELIEVE Ulquiorra will return? (Check all boxes that apply).
No, the guy blew away in the wind.
Yes, no one ever dies in Bleach, least of all such a popular character.
Oh NO, he finally understood the heart, had a great death scene, end of story--he said himself it would "never end" unless he died! Is he supposed to keep fighting the main character until the end of the manga! HOLY TEDIUM!
Yes, he still has to throw Lanza Del ReLampago successfully--shounen characters are never given a weapon to have it fail on its first try without it being used successfully another time.
Yes, because Morita-kun asked Kubo if Ulqui was dead at Jump Festa and Kubo was coy and Kishimoto was the same way about Kakashi last year and we know Kakashi came back from the dead.
No, because Kubo is just a tease and will say anything to placate his fanbase but he loved the death scene and it was voted favorite scene of the manga at Jump Festa and why ruin a good thing like that?
Yes because there's money in that there Emo Espada and Jump knows it.
No, because Kubo won't compomise his manga by letting all these secondary characters take it over--Ichigo's popularity is already slipping!
Yes because Kubo always planned Ulqui's return. Ulquiorra appears to be an homage to Vegeta who also turned to ash and returned from the dead as a villian redeemed.
No, because Kubo has too much other story to tell and his editors won't let him bring back stuff to drag down the pacing further--they cut out the Menos Forest and Ashido and the Zanpakutou arc remember?
No, because I willed it with my mind. Kubo is very susceptible to my telepathic energy.
Yes, because the fans (even in Russia!) are writing Kubo letters begging for Ulquiorra's return!
Other (explain in comments)
I believe in Ulquiorra's return. I believe that Kubo-sensei planned his return before Ulquiorra left--that's why Ulqui didn't get a flashback, didn't get to ruminate further on what a heart is (he merely realized the idea as in "oh there!" which is lovely and poetic but knowing Kubo, there's usually more), and why Ulqui didn't throw Lanza del ReLampago successfully (my dear LB7-sensei was fuming about the scene and wondering why Kubo made it look like Ulqui needed bifocals--WHY miss? To only shoot successfully, say I, in the grand shounen tradition). Other reasons why Ulqui will return include that he's a wonderfully exploitable character--his suspicious nature makes him endlessly unfathomable so one may never really be sure whose side he's on, his relationship with Orihime seems to have caught fandom by fire and all artists and businesses love this sort of thing in an audience.
Also, Ulquiorra's death was by far the most beautiful death in Bleach I've seen so far but it isn't the closing sentence on the heart theme. Hearts, as far as we understand them in Bleach so far, do not exist merely between a dead friend and a living one, such as in the dynamic between Kaien and Rukia introduced in the Arrancar arc. Orihime spoke of hearts in tower, Aizen spoke of hearts in recent chapters, and the heart theme, like Ulquiorra, I believe, will return again to Bleach.
ETA: Aaaaand Alex made me remember two of the other main reasons I believe Ulqui is coming back.
1) because Orihime needs to show off her tremendous powers of bringing back something from nothing (like Hacchi did with Tsubaki).
2) (can't believe I forgot this one), I don't like the idea of a shounen hero having blood on his hands. Ichigo KILLED Ulquiorra against all the codes of civil warfare, when Ulqui was already disabled, and it wouldn't make any sense for Ichigo to atone for that without things being made "all better by the dragonballs." This IS shounen.