You might like to have a read of this
http://www.wiltshire.gov.uk/archaeological-research-agenda-avebury.pdf
I've just cast my eye over the beginning chapter very quickly but it stands out that the plan is to undertake excavations only in a disciplined way where it fits into proper research. And that research has to be done in a sustainable way ie "meeting today's need for improved knowledge and understanding of the WHS without jeopardising the ability of future generations to do the same". So I reckon that doesn't include reerecting all the buried stones just to satisfy the aesthetic sensibilities of visitors. Whereas maybe excavating the beckhampton stones finally proved something major that hadn't been proved before
(the resistivity surveys weren't conclusive
http://www.eng-h.gov.uk/reports/beckhampton/ )
ie that the avenue really did exist.

Anyway I dunno, why don't you email Josh Pollard and Mark Gillings, then you won't have to speculate.