In regards to Haste specifically, the stats surrounding the spell were created for a single target in mind, so for balance reasons we have no plans to make it possible to turn it into an AoE spell.
Virtually every other spell that was only available as single target "for balance reasons" was eventually made AoE by SCH and /SCH

Haste being single target only is not a balance issue, it's just a hassle, and it's one of the reasons some people I know stopped playing WHM.