According to poll conducted at Biglobe website, upcoming idol sci-fi anime series AKB0048 topped rankings on most anticipated anime series to premiere this April.

Anime series Fate/Zero Season 2, Hyouka , Kore wa Zombie desu ka? OF THE DEAD and Haiyore! Nyaruko-san which also air  this April, were also in the top 5 list.

Rankings

1. AKB0048
2. Fate/Zero 2nd Season
3. Hyoka
4. Kore wa Zombie Desu Ka? OF THE DEAD
5. Haiyore! Nyaruko-san
6. Accel World
7. Saki – Achiga-hen Episode of Side-A
8. Medaka Box
9. Kimi to Boku 2
10. Shining Hearts: Shiawase no Pan
11. Natsuiro Kiseki
12. Shirokuma Cafe
13. Tasogare Otome x Amnesia
14. Kids on the Slope
15. Eureka Seven AO
16. Hiiro no Kakera
17. Kuroko no Basket
18. Phi Brain: Puzzle of God 2nd Season
19. Tsuritama
20. Sengoku Collection
21. Queen’s Blade Rebellion
22. Upotte!!
23. Sankarea
24. Uchū Kyōdai
25. Nadia: The Secret of Blue Water

Survey was conducted between March 26 to April 2 with 10,010 votes casted.

[Source]