Would an AIO for an i7-6700K fit a i7-8700K?

[King Mustard]

They're both LGA1151, so I presume so but it's best to make sure.

Would it require a different bracket or anything?

 

[pastymuncher]

Sockets 1150/1151/1155/1156 all have the same spacing so the cooler still physically fits. Is it a decent cooler as the 8700k is a fairly warm running cpu, especially when overclocked? I wouldn't be going from a 6700k to a 8700k though. The performance gain will be tiny for the price you will pay for the 8700k and a new board. If you need more cores I would be waiting to see how good AMD's new cpu's are in a couple of months.

 

[doyll]

As already posted, all 115x have same mount spacing (75mm x 75mm square)