[kemo]

Kohana isn't a CI rewrite since 3.0.0. And yeah, Kohana 3.3 will natively use 5.3 goodies.

[eropple]

I've yet to see any indication that it will use PHP5.3 in an idiomatic way. It still seems like a bolt-on.

(I still wouldn't use it because frankly, I don't think the Kohana developers take security seriously enough, but it'd be a start.)