I take your point, but if they've already deferred a substantial amount even their status as preferred creditors might not be enough. Also, if the club's going tits up over the summer anyway they won't be lose out by agreeing to leave. Clearly the club can't continue in League 1 paying Ben Haim et al.
It seems to me that the players are faced with a choice between 1) negotiating a transfer whilst still in Pompey's employ and 2) seeing the club cease trading leaving them without a contract. Given that, there's surely no real reason for the high earners to stay on as, if sold, they're not going to command a fee which would impact on their earning power at their new club.