Horner knows Ferrari are in trouble and is sticking the knife in. He's a clever bloke.
I can definitely see Vettel eyeing up a move if Ferrari show no signs of progression and given that they've failed to produce a car at least on a par with the best since 2008, through two complete regulation overhauls, wouldn't give me much confidence that they'll achieve it this time round.
They just don't learn, there's always a fall guy. Chris Dyer was sacked for the Abu Dhabi mis-hap in 2010, Aldo Costa was binned off and has since worked wonders with Mercedes in the engine department, Tombazis was sacked off as head of aero and nothing has changed there, Pat Fry came in and was removed when Alonso departed. Allinson was meant to be the savior, yet they've regressed again since last season. I imagine his tenure won't last much longer if they're still muddling around next season.
Arrizabene was outrageously harsh towards Alonso when he decided he'd had enough when you consider that he pretty much single-handedly made the team look respectable for five seasons.