According to Aviation Week and Space Technology, Boeing thinks that
this is a near-even trade-off. However they believe that
electro-mechanical system will advance more quickly than bleed air
stuff, and that 20 years from now the tradeoff will be heavly away from
bleed air. They are moving now because they want to get a jump ahead,
and because future models of this plane will probably be getting new
equipment in 20 years.

-Kitplane01