"a much pleasanter reason"

[Hagrid]

No: HPFGUIDX 131074

In "the Snitch" site, they give different things coming up in HBP 
http://www.thesnitch.co.uk/site/index.php?class=The%
20Snitch&page=Book%20Six%20::%20Facts

One says:
Harry Potter's stay at the Dursley's will be the shortest yet; this 
will not result from another court case, since he will be leaving 
for "a much pleasanter reason." 

I suggest it may be APPARATING lessons.

Just as Fred and George passed their apparating tests outside of 
Hogwarts during the summer holidays, summer may be a good time for 
lessons to be held.

I assume apparating rules are similar to muggle driving rules - a 
youth can learn to drive even before he/she is old enough to get 
their license.

Likewise, Harry can't sit for his apparating test till Book 7 (I 
think) but lessons may still be available to him now.

Besides, going to apparating classes with Ron and Hermoine would be 
as fun as going to the Quidditch World Cup in GOF.

aussie_lol