I wouldn't be surprised if the contact icons will be removed in future versions.
If an Admin has several of them enabled and you look at the Members page it looks a bit messy.
There are so many new contact ways popping up that as soon as phpBB adds more there'll be something new to add.
I think the future for external contact links is going the way of Slink
, it removes the burden of having to update the contact page on every forum or website that you use just because you changed your Twitter handle etc.