Do you mean more 'home screens' than the default five? If so then the ability to add more is already there; long-press on the screen, and when it goes into 'Edit mode' simply scroll the screen list to either end and press the + button to add another screen there.

 

Seven is the limit for Xperia Home. Nova allows nine.... dunno about alternative launchers.

 

I can confirm that 9 is the limit for Apex too.

Go Launcher used to allow more, but they reduced it to 9 (iirc) at one point. Not used that one in 18 months, so no idea what it is currently.