It's all speculation at this point, I'll believe it when it happens.
Besides it wouldn't be advantageous for RBR to sign an experienced driver as Number 2, I don't think Vettel would approve of the threat to his Number 1 spot, but on the other hand, it would give him an excuse to disobey team orders and show his true selfish egotistical nature again.
Webbers F1 days are definitely done after 2013 I think.
Cheers