I am not sure about them joining the EU, it is already too big. Perhaps NATO because we could do with some of their muscle to help us out in Afghanistan, since most of our other NATO members seem too afraid to pick up a weapon.
Politically, in all areas, for Israel, it makes a lot of sense, but I doubt it;ll happen, they'd bring to much baggage, and would appear to the Arab world as if the west was as good as declaring war on them.