We won the war for independence (the war of 1948) and got the 1949 borders. The most I can see is in an absolute Israeli wank in which Israel annex southern Lebanon till the Litany river if we mange to conquer it. If Lebanon never had the south then Israel got a better claim to it, as it is traditionally considered the northern border of the land of Israel. If this happens then yes, Lebanon will surly seek an alliance with israel in order to be saved from syria, now the israel and Lebanon have a common border.