I believe for consumer laptops, they will probably use HDMI, while higher end business orientated laptops would most likely have Mini DisplayPort. Lower end business orientated laptops might just include VGA instead of Mini DisplayPort. Because consumer nowadays will most likely connect to a HDTV or HD monitor rather than a projector, while business orientated people will use HDMI or VGA.
DP is best, of course, but I'll be thankful if they use HDMI and skip VGA. Many business-oriented laptops, like zy pointed out, still use VGA because they want to be able to support the old, old projectors still being used by many businesses.
HDMI is good but most meeting rooms are still fitted with just VGA cables even if the projector supports HDMI. But thankfully most newer meeting rooms are now fitted with HDMI cabling too. at least here in SG.