The big question in Guatemala following Monday's military coup is whether anything has really changed. Brig. Gen. Oscar Humberto Mejia Victores, Guatemala's new leader, is very much the country's archetypal military man. Extremely loyal to the military establishment, he wants to keep it intact. A hard-liner on dissent, he favors crackdowns against those opposing the military.
In seizing power, however, General Mejia Victores made the usual pledges to hold elections soon and to promote democracy. And he is likely to speed up the timetable for elections to bring civilians back into government, perhaps scheduling the vote for a constituent assembly as early as January or February of next year and presidential balloting by the end of 1984 or early 1985.
But there is little to suggest that Guatemala under General Mejia Victores is headed for truly democratic rule after three decades of on-again, off-again military rule - some of it quite brutal and repressive. He indicates that he expects the military to play a continuing role in governing the volcano-girt nation.
The Reagan administration is adopting a wait-and-see approach, giving what one official termed a ''cautious endorsement'' of the new Guatemalan government. US Ambassador Frederic L. Chapin met with General Mejia Victores at noon Tuesday in what Washington termed an ''informal'' session.
With the controversial US-Honduran military maneuvers just getting under way in neighboring Honduras, Washington is casting a wary glance at Guatemalan developments. The US sees a stable Guatemala as a key to US policy pursuits in Central America and hopes this week's coup will not put that goal in jeopardy.
Meanwhile, General Mejia Victores promises ''an all-out fight to eradicate Leninist-communist subversion, which threatens Guatemala's liberty and sovereignty.''
What that means can only be guessed at.
Given his reputation for hard-line solutions, Mejia Victores is expected to vigorously pursue an antisubversion policy that in recent years has led to the deaths of thousands of civilians. A close associate of the general says: ''We're in a war with communism and in wars a lot of innocent people die.''
That is a far cry from the attitude of ousted President Efrain Rios Montt. Although he was often accused of supporting longstanding policies that violated human rights, he is also credited with adopting policies that limited some of these violations.
It is understood that Mejia Victores, who was defense minister under Rios Montt, felt his predecessor was soft on ''the communist threat,'' a phrase he frequently uses. The new President was deputy defense minister in an earlier government, and in that post helped draft some of the antisubversion policies that he now promises to pursue.
Rios Montt's ouster may have been sparked as much by personality differences as by policy differences. Rios Montt is a self-proclaimed born-again Christian who named religious fundamentalists to key positions. That angered many officers , including General Mejia Victores. How much this weighed in the ouster is unclear.
The new leader enjoys the support of the military establishment - support Rios Montt lost in recent months. In a nation dominated by the military, such support is essential and should make consolidation of power easier.