Dudley: Muggle or Wizard?

[Boolean]

No: HPFGUIDX 134753

Boolean:
One thing struck me when reading Chapter 3 of HBP again, which I hadn't 
properly picked up on the first time is what Dumbledore says to Petunia 
and Vernon about Dudley. 

Unfortunately I'm at work and don't have the exact quote to hand (if 
someone could oblige...!?) but he is admonishing the Dursleys for not 
treating Harry as though he were their own. He then says something 
along the lines of, mind you, look how badly you've treated Dudley. On 
reading it for the first time I just assumed he was referring to his 
being spoilt rotten, but then I noticed that Petunia was reacting 
strangely and this led me to wonder if, in their all-consuming fear of 
all things magical, Dudley hadn't shown signs of wizardry in his early 
years which were covered up. Is it even feasible that they got a letter 
inviting Dudley to Hogwarts? 

I admit that it seems unlikely, I just thought DD's comment was rather 
cryptic...and although there's only 1 book left to go I am still 
holding out hope that one of the Dursleys will turn out to have magical 
qualities!