My disagreements with this argument;
1. The claim that box office needs 4 x the production budget to be get a sequel is just a theory.
* We can test the theory of when studios approve sequels by looking at the numbers and seeing when sequels are approved. (From the numbers.com website)
http://www.the-numbers.com/movies/franchise/X-Men#tab=summary
- May 26, 2006 X-Men: The Last Stand, production budget: $210,000,000, worldwide box office: $459,359,555, ratio box office/budget = 2.19
Sequel approved.
- May 1, 2009 X-Men Origins: Wolverine, production budget: $150,000,000, worldwide box office: $374,825,760, ratio box office/budget = 2.49
Sequel approved.
- Jun 3, 2011 X-Men: First Class, production budget: $160,000,000 worldwide box office: $355,408,30 ratio box office/budget = 2.22
Sequel approved.
So, that's two franchises (Star Trek & X-Men) where sequels were approved with box office being about 2.5 x the production budget or even less.
I could find more examples.
2. A movie makes money from more than just theater box office. There are disk sales (DVD/Blu-ray), streaming, cable broadcast fees, and with science fiction there are merchandising fees from toys and comics.
** Back to "Covenant"; a sequel could happen if its box office gets to 2.5 the production budget. Why? Because there are multiple movies which got sequels (like Batman Begins, Star Trek, X-Men) where that kind of performance got a sequel.
3. The Alien franchise is considered to be one of the top science fiction movie/TV franchises of all time.
http://screenrant.com/greatest-science-fiction-franchises-ever/
The challenge for the Fox studio is to figure out how to release an Alien franchise movie which can get better box office.
Whether the studio goes with a film more like "Prometheus" or "Aliens", there is the potential to make money and because of that, the Alien franchise is not dead.

The point isn't that a sequel requires revenues at up to four times the budget.
My point is that you and I are not studio executives.
Another of my points is that all we can know if our theories about sequels are correct is by what past box office/budget performance can lead to a sequel.
* Besides, several Star Trek and X-Men movies (and Batman Begins) getting sequels approved with box office ~2.5 x (or below) the production budget, there are other moves where this happened.
- From the-numbers.com
- Jan 20, 2006 Underworld: Evolution, production budget: $45,000,000, worldwide box office: $113,417,762, ratio box office/budget = 2.5
Sequel approved.
- Jan 23, 2009 Underworld 3: Rise of the Lycans, production budget: $35,000,000, worldwide box office: $89,102,315, ratio box office/budget = 2.5
Sequel approved.
- Jan 20, 2012 Underworld: Awakening, production budget: $70,000,000, worldwide box office: $160,379,930, ratio box office/budget = 2.3
Sequel approved.
- A straight comedy movie, Analyze This, Production Budget: $80 million, Worldwide box office: $176,885,658, ratio box office/budget = 2.2 (from Box Office Mojo)
Sequel approved.
- I've already mentioned "AVP". It's box office was above 2.5 x the production budget but it's below 3x at around 2.87.
Sequel approved.
The Alien franchise is one of the best, but that's not shown in the two recent releases.
We all are entitled to our personal taste about any film.
- But our personal taste should not be part of this discussion. (Individual personal taste does not = professional critic rankings or large viewer polls.)
The personal taste of a few individuals has nothing to do with the fact that several movies exist which got sequels that had box office which was about 2.5 x their production budgets.
- As for the box office for "Prometheus", it was 3.1 x its production budget. And it got a sequel. Many films get sequels when their box office is 3 x the production budget.
And comparing "Prometheus" box office with some other Alien franchise films?
- Alien3 - production budget $50 million, world wide box office, $159 million, ratio box office/budget = 3.18
Sequel approved and "Prometheus" did about the same with its box office / budget performance.
- Alien Resurrection - production budget $75 million, world wide box office, $161 million, ratio box office/budget = 2.15
Sequel not approved.
But both "Prometheus" and "Covenant" have outperformed Resurrection.
* Bottom line; again, going by the publicly known facts about film history, box office and production budgets, if the box office for "Covenant" gets to 2.5 x its production budget, it could get a sequel.