If QPR come back up, then he may end up back at his parent club but QPR have absolutely no power to stop Newcastle activating that release clause whilst they're registered as a Championship club. Furthermore, from what I'd assume, that £2m fee that Newcastle paid will stop any other club being able to negotiate with Loic Remy before he is re-registered with QPR, the same as BMW can't take my company car off me, even though they own it, effectively it's my property until the contract says it's theirs again. Looks water tight to me.
There's always the possibility of other clubs whispering in his agents ear, probably Liverpool since that's how they go about their pathetic signings, but contractually there wouldn't be a lot more that Newcastle could do to have him, whilst covering themselves from any possibility with his rapey allegations.
The difference between this loan and the Welbeck to SAFC loan is that Fergie never allowed for an option to buy, whereas Harry Redknapp has no say in the matter.