Ronaldo missed the match in Porto because of suspension — but in his absence, Portugal ensured he would have the chance to appear at a record sixth World Cup.
The five-time Ballon d'Or winner will be 41 by the time the tournament kicks off next June, with Ronaldo having said recently it would be his last shot at winning the one major title to elude him.
Assuming he retains his fitness, he's expected to be part of coach Roberto Martinez's squad, though he may yet be suspended for as many as two matches after being sent off in Portugal's 2-0 loss to Ireland on Thursday.
That surprise defeat meant Portugal had to beat Armenia to be certain of top place in Group F and hat-tricks from Bruno Fernandes and Joao Neves ensured there would be no slip-up.
Hungary had the chance to overtake Portugal at the top of the group, but fell to a stunning late comeback from Ireland - losing 3-2 in Budapest.
Troy Parrott scored a hat trick — with an equaliser in the 80th minute and the winner coming in the sixth minute of time added on. Victory meant Ireland finished in second place and will advance to the playoffs.
Both Ronaldo and his great rival Lionel Messi will appear at their sixth World Cup if they take part in next year's tournament, thus surpassing greats like Germany's Lothar Mattheus, who appeared in five.
Defending champions Argentina have already secured their place, with Messi having fulfilled his career-long ambition by leading and inspiring them to the title in Qatar in 2022.
Ronaldo led Portugal to the Nations League earlier this year and last month became the leading scorer in World Cup qualifying games with 41 goals.
There was no shortage of goals from Portugal in his absence on Sunday, with Fernandes' hat-trick including two penalties. Neves struck twice in the first half and completed his treble with a goal in the 81st.
An unforgettable week for Ireland was capped off with a dramatic fightback in Hungary and a place in the playoffs.
Parrott's late winner was his fifth goal in two games to seal second place for the Irish and it came after he'd struck both goals in the 2-0 win over Portugal.
With Ireland trailing 2-1 going into the 80th minute at the Puskas Arena, the Dutch-based AZ Alkmaar player proved his country's hero again.
First, he lifted the ball over Hungary goalkeeper Denes Dibusz to level the match at 2-2 and with the clock running down, he converted from close range for the winner deep into added time.
In Tirana, England completed a perfect World Cup qualification campaign as Harry Kane's late brace secured Thomas Tuchel's side a 2-0 win -- an eighth victory without conceding.
They completed their group K program by becoming the first European side to play at least six World Cup qualifiers and win them all without conceding.
Having also already qualified, coach Didier Deschamps fielded a second-string French side, who overcome a nervous start to win 3-1 in Azerbaijan, with goals from Jean-Philippe Mateta and Maghnes Akliouche, and an own goal from Shakhruddin Magomedaliyev.
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