Philip Habib's energetic diplomacy appears ready to bear fruit. The Lebanese and Israeli Cabinets have approved the PLO evacuation plan and the exit of the fighters is imminent. If all goes according to the carefully conceived scenario - with multinational troops stepping in as the guerrillas leave - Lebanon's sympathizers will breathe a sigh of relief that the city of Beirut has been spared further suffering. While the United States should never have tolerated the Israeli seige to begin with, it is at least - through the skillful, tenacious efforts of Mr. Habib - making the best of a bad situation.
The evacuation, if successful, will solve the immediate problem. But there can be no euphoria in Washington as policymakers look beyond the evacuation to a whole tangle of problems that demand urgent attention.
There is the question of Lebanon, trying to carry on a political process amid the turmoil. The election of a new president by parliament has been postponed, but under the constitution it must take place by Sept. 23. With only one candidate announced - Phalange leader Bashir Gemayel, who is disliked by Muslims - the election would be a farce and could hardly be expected to achieve the Muslim-Christian consensus required for Lebanon's confessional system of government.
Looming over the election is the Israeli and Syrian presence and the risk of a de facto partition of Lebanon. Israel's avowed aim is the establishment of a strong central government in Beirut, but in Israeli terms that means a ''friendly'' Christian-dominated government, not one worked out by consensus and reflecting the ethnic, racial, and religious balance in Lebanon. There now are reports from southern Lebanon that the Israelis are letting Christian militia units challenge the authority of the regular Lebanese Army. If Israel undermines such a needed national institution as the army, how is it possible to forge a ''strong central government''?
At stake is Lebanon's sovereignty and territorial integrity. It is no secret that some Israeli leaders envisage southern Lebanon as a part of a Greater Israel or favor a virtual partition of Lebanon through proxies - a partition which some believe Syria may already have tacitly agreed to. Will the US acquiesce in such a development, just as it has passively acquiesced in Jewish expansionism in the West Bank, in annexation of the Golan Heights, and in the invasion of Lebanon? Even with strong US leadership, however, will it be possible to save Lebanon's independence if the Lebanese themselves, split into so many feuding religious and political factions, do not put their disputes behind them and rally to hold their country together?
Then there is the question of the Palestinians and their future. Diplomatic corridors resound with talk of how much the PLO has lost or won as a result of the Israeli onslaught. No one knows how the political organization will evolve with thousands of its troops dispersed (and thousands still to remain in northern Lebanon). But there is no denying the growth of Palestinian nationalism and the need to address the fate of the Palestinians both in the West Bank and in the diaspora.
Some expect official Israeli policy in the West Bank to harden now, despite encouraging evidence that the majority of Israelis would like an accommodation with the Palestinians (whose determined stand in Beirut has won them grudging respect). Much will depend on how vigorously the United States presses for an overall settlement. The problems are formidable, not least of them Egypt's refusal to rejoin the stalled Camp David negotiations until Israel withdraws from Lebanon. But it can be hoped that Washington will not wait for a total solution to the anguishing problems in Lebanon before tackling the West Bank issue.
Mr. Habib deserves the world's tribute as a diplomatic superman of sorts. But, as the PLO fighters leave Beirut, let it not be thought that a major US foreign policy victory has been achieved in the Middle East. That has yet to be accomplished.