Hmm...Israel participating in the attack is far-fetched but cannot be ruled out entirely.
After all, they know that Pakistan will strike back at India immediately but not attack Israel.
Israel will prove to its citizens that it has the b*lls to
avenge the rabbi couple murder, and do it in a low-risk fashion. Their citizens are disgusted at their govt for its perceived weakness:
failure in the Hezbollah war, failure to rescue Gilad Shalit, being forced to release convicted killers (e.g. Post-Mumbai, many Israeli citizen blogs praised Mumbai commandos for killing the terrorists rather than negotiating with them and compared them to their govts weak stance on hostages like Shalit).
The govt is desperate to show that it means business (e.g. both PM candidates Livni and Netanyahu have promised to oust Hamas from Gaza) and what better way to show it...
I know the above sounds a bit like a Tom Clancy novel, but I would not rule it out entirely...