In answer to the poll - no, Madeleine is not alive. In my opinion she died either from two reasons - sedation gone wrong (the most likely) or that she was hit/pushed/shoved too hard probably by Kate through stress/exasperation/exhaustion.
I believe the abduction was simulated and Madeleine's poor body was hidden because the Post Mortem would have shown up the sedation drugs or evidence of abuse, or both.
I think the Tapas group all know what happened, with the exception of Diane Webster. They are in on it because they were also sedating their kids, if found out, they would lose their medical careers and have their children taken into care.
As for where Madeleine is, I believe they put her out to sea and her body will never be found.
To be frank, I can't bear the sight of Kate or Gerry, I find them despicable. I hold much hope that they'll be bought to justice one day, and I believe this will happen eventually.