After Trudeau

Canadian Prime Minister Pierre Elliott Trudeau has always had a strong flair for the dramatic - and for political timing. Both qualities were very evident this week when Mr. Trudeau announced plans to step down after more than 15 years as head of his nation's government. Mr. Trudeau's departure comes at a good moment for Canada, as well as for himself personally.

Canada is ripe for change. Although its economy is showing an upturn from the recent recession, along with those of most other Western industrial nations, there are still many challenges. Unemployment, while stabilized, remains high. Many western Canadians continue to feel that the national government at Ottawa - and particularly Mr. Trudeau - is insensitive to their interests. For such reasons political analysts believe that the opposition Progressive Conservative Party of Brian Mulroney now has a solid shot at winning the next national election, expected to take place later this year.

Were the election to occur now, Mr. Trudeau's Liberal Party, according to polls, would be defeated.

By leaving office during the next few months, both from his post as prime minister and leader of the Liberal Party, Mr. Trudeau can bow out with his head held high. He can always look back on his long tenure in office, hold his thumbs up, and say: ''I held it all together.'' And the party benefits by gaining a new leader, perhaps John Turner, the former finance minister.

For all the faulting of his economic policies, Mr. Trudeau's major accomplishment would have to be considered his work in championing the cause of Canadian national unity. That drive for unity came at a time when separatist pressures from the Quebec provincial government of Premier Rene Levesque were particularly intense. Forever seeking broad areas of compromise between French- and English-speaking Canada, it was Mr. Trudeau's government that pushed through the bilingualism policy making French an equal language with English, as well as patriating - i.e, bringing home from Britain - the Canadian Constitution. That decision sundered Canada's colonial links with London.

Despite its problems, Canada is in about as favorable an economic position - relative to other Western nations - as is possible at this point, given its current high unemployment. The New York-based Conference Board now puts Canada's leading economic indicators ahead of Western European nations, and only slightly behind Japan and the United States. And growth figures just released this week by Ottawa showed that the Canadian economy grew by 3 percent last year. That compares with a decline of 4.4 percent in 1982.

Whichever government assumes office in a new election, it is expected to be more center-to-right on economic policies than the center-to-left orientation of Mr. Trudeau. That means that the government can pursue more growth-oriented economic policies, including greater tolerance toward US economic investment in Canada, than has been evident in recent years.

Meantime, it seems highly unlikely that Mr. Trudeau will fully disappear from Canadian political life. A top United Nations post cannot be ruled out. He remains dedicated to seeking greater cooperation between East and West, including a genuine disarmament.

From the time back in the late 1960s, when he electrified his nation's politics and made ''Trudeaumania'' an international symbol of the new Canada, Mr. Trudeau has confounded his critics. In that regard, it seems safe to say that he will continue to fulfill a major role in Canadian and world affairs.