The veil may not be death at all....... Jk has not been very clear about Sirius being dead, always avoided the topic.... I think the veil is something nobody understands, as anybody who touches it probably gets sucked in...... The voices make a very clear point that they are not dead, Exist in some form inside the veil.... May be it just imprisons everybody who goes through it with no way to get out, The veil must have been in existance for a long time which might explain the number of voices....... and besides If Jk wanted to kill Sirius she could have made Sirius fall through the veil and fall out through the other side dead! why did she make him vanish??? I still think harry and sirius will communicate in some way!!! Lets see what happenes in book 6.