Let Square don't hear you, Spritz. I hope there are -at least- 20 summons. I still think there are way too few summons in FFX...
Let's see...the ones I personally want are:

-Bahamut (obviously)
-Alexander
-Leviathan
-Ifrit
-Shiva
-Quetzacoatl (though I think this is gonna be Ramuh)
-Maduin
-Odin (with real attacks please, not only one-hit killing-or missing- ones)
-Gilgamesh
-Carbuncle
-A new one that looks like Anima
-Titan
-Diablos

And I entrust the rest to Square...I hope there're cool new ones...