Here are how the numbers for the game break down:
On average, the publisher receives $27 USD for every $60 game sold. Perhaps a bit more for pre-orders, etc. At a reported cost of $267m USD, the game would have to sell 9,888,889 units to be profitable. This is actually very likely to happen, as reportedly, GTA IV sold somewhere around 22m units.
Even if the game is bad, and even if the game's sales suffer, considering the series' past sales and the amount of media exposure this seems likely.
However, keep in mind this is one of the most competitive falls in video game history. MGS5, Titanfall, Destiny, Watch_Dogs, Assassin's Creed 4, CoD Ghosts, Battlefield 4, and two next-gen systems are competing for the consumer's money. This is not even to mention games like Legend of Zelda: Link between Wolrds, Knack, GT 6, etc, which all look good, though they may not directly compete with the more adult enthusiast-oriented titles above.
If GTAV is simply buggy and boring, plus if these other titles conspire to reduce its sales, it could spell trouble for Rockstar and Take-Two, as they would not be able to fund many new titles in the coming years.
Edit: Also, price drops on the Vita and the new 2DS could entice parents to buy those for their kids instead of spending money on GTAV.
Here are how the adult-oriented series break down in sales:
MGS: About 6-7 million units
CoD; about 10-15 million units
Assassin's Creed: varies between 2m for Brotherhood and 6m for AC3
Titanfall, Destiny, and Watch_Dogs are all new, but Ubi is already planning for much future W_D content.