IF the parks got sold off, their success would pretty much be depending on WHO got them... I'd be more optimistic for Chessie's future under Plopsa then say Parques Reunidos (although I'm sure many would not be happy by the further cookie cutter areas that Plopsa would provide) because it would suit their market perfectly...
HOWEVER, Thorpe under Plopsa would be completely wrong and arguably suit Parques Reunidos better... I think herein lies the rub, as it's unlikely that Merlin would sell them all off individually (and I also doubt they'd want rid of Legobland), so would there be an individual company willing to take on 3 parks where 2 of them desperately need high levels of reinvestment in infrastructure?