When Anheuser-Busch InBev approached SABMiller last week about a potential takeover, it set in motion what beer analysts have been anticipating for years: The creation of what some have dubbed MegaBrew, the joining of two brewing giants that today control more than 30% of the world's beer market, according to Euromonitor International. (See graphic below; China's Snow brand is a joint venture between SABMiller and China Resources Enterprise.)

"In the world of brewing M&A activity, this is truly the title fight, the one that determines the World Champion," wrote industry trade publication Just Drinks. "And, most likely, this will be forever and ever, for the combination of the world's number one and two brewers will be a monster."

Here is what the deal could mean in adland, and beyond:

Why is this happening now?

This deal has been speculated about for years, but several forces have aligned to make the timing right, according to analysts. SABMiller's stock price has been weak, making a takeover more affordable. Interest rates are low, making borrowing cheaper. Also, the operators of A-B InBev are known more for their financial chops than their brand-building prowess. Mergers and acquisitions is just what they do -- and it might be the only way to grow the bottom line in an era in which big brands like Bud and Bud Light have struggled to grow volumes in developed markets like the U.S.

What does it say about the state of Big Beer?

"Beyond the financial and cost savings side of such a potential deal, there is little doubt that macro-beer is now gazing at the event horizon of the merger and acquisition era," Spiros Malandrakis, senior alcoholic drinks analyst at Euromonitor, said in a statement. "As the craft movement is coming of age and solidifies its position as a key disruption force within beer and the entire alcohol industry, corporate consolidation can perhaps provide some last drops of stock market intoxication." But the deal-making "will remain largely irrelevant to the scores of millennials seeking alternatives to big beer's offerings. Innovation and small scale experimentation will decide future growth trajectories if not respective size and margins."

Just how tough is it for Big Beer? Consider that since InBev bought Anheuser Busch in 2008 to form A-B InBev, the U.S. volume loss on Budweiser is "the equivalent of every legal drinking age consumer within city limits of Chicago giving up almost one six-pack of A-B products per day, every day of the year," Carlos Laboy, an analyst for HSBC Global Research, stated in a report last week.

What would a merger mean in the U.S.?

In the states, A-B InBev and MillerCoors (which is partially owned by SABMIller) control roughly 70% of the beer market combined. So to soothe anti-trust regulators, A-B InBev would almost certainly have to offload the MillerCoors brands. The most likely scenario is that Molson Coors, the other owner of MillerCoors, would buy a full stake in the joint venture. There is one wildcard: Some analysts have cautioned not to rule out Heineken and SABMiller hooking up in order to ward off A-B InBev's takeover of SABMiller. That would potentially put brands like Heineken, Dos Equis and Miller Lite in the same ownership house, assuming regulators would not take issue with that.

How would MillerCoors change if it were solely owned by Molson Coors?

MillerCoors has been hampered by the fact that it has to get consensus from two owners on big decisions, according to multiple people familiar with the brewer. "The two partners haven't always agreed on everything. That is well known," said Benj Steinman, president of beer trade publication Beer Marketer's Insights. "There's no doubt that integration into a single owner will be beneficial to MillerCoors decision making," said a former MillerCoors executive. MillerCoors declined to comment for this story.

But what decisions would a Molson Coors-owned MillerCoors make?

It is possible that Coors brands could gain favor over Miller brands because of their historical ties to Molson Coors. After all, Pete Coors -- the great-grandson of Coors founder Adolph Coors -- is a vice chairman of the Molson Coors board. Still, Miller Lite has had more momentum than Coors lately, so it's doubtful Molson would want to disrupt that. Even so, "Coors Light is larger than Miller Lite in both the U.S. and worldwide," said the former MillerCoors exec. "Molson Coors will likely prioritize based on that, the ROI on spend specific to each brand, and whether or not it owns the Miller trademark elsewhere in the world once the M&A dust settles."

What about A-B InBev, how would they behave in the U.S.?

"I don't think it changes anything. They are going to keep trying to resuscitate Bud," said a former A-B InBev employee. But this person added that "it may slow down some of the increases in the brand support because they are going to have to pay the debt off [incurred by the deal]." And some analysts have suggested the merger could prove a distraction. If the deal goes through, the U.S. moves from 36% to 27% of A-B InBev's operating profit, according to a report by analyst Chris Pitcher of Redburn that was cited by Beer Marketer's Insights. That's positive since it "dilutes a market that is currently underperforming from a market share perspective," according to the report. But it could also cause concern "because it would dilute management focus at a time when stabilizing A-B InBev's market share in the U.S. is one of the main priorities."

What would a merger mean for ad agencies?

In the short term, probably nothing. Assuming A-B InBev can strike a deal, the transaction likely wouldn't close for many months, as the brewer winds through thorny regulatory issues. In the long term, all bets are off -- especially globally, where multiple brands would have a new owner. But in the U.S., there seems less of a chance for major changes as long as MillerCoors exists as an entity overseeing Miller Lite and Coors Light and A-B InBev 's current crop of U.S. marketing execs remain in place guiding Bud and Bud Light. And there is no reason to believe anyone is going anywhere right now.