There’s little doubt that the market likes the prospect of what a partnership with The Coca-Cola Company (KO) could do for Green Mountain Coffee Roasters (GMCR). When Green Mountain announced last week it would be building a soda-making appliance capable of mixing Coke’s famous carbonated flavors for at-home consumers, KO stock brightened up a bit, while shares of GMCR stock jumped 26% in one day.

And why not? Ten years ago, single-serve coffee brewers were a rarity, even in offices. Now single-serve coffee makers are common, so much so that Green Mountain Coffee Roasters sold 9.8 million of the famous Keurig brewing machines and 8.3 billion single-serve coffee “pods” last fiscal year. If they can make something out of nothing for coffee, why couldn’t they do the same for soda?

As is always the case, though, there’s a flip side to this coin — particularly for Coca-Cola and KO stock.

This endeavor might not be the game-changer many seem to think it could be for the carbonated beverage industry … for three reasons.

1. The Keurig Cold solves a problem that doesn’t exist, and in so doing, creates other problems.

Clearly the success of Keurig single-serve coffee brewers has stoked optimism among GMCR stock holders that the same kind of demand could be whipped up for a Keurig cold/carbonated drink maker. But that might be an overly optimistic assumption.

See, the single-serve coffee brewers do something that isn’t easy or convenient to do, eliminating the annoying aspects of coffee. Coffee is usually enjoyed hot (and heating water can take time), and even though most coffeemakers only make a pot of coffee, most coffee drinkers only need one cup of java … not four or more cups. Keurig brewers make one cup of hot coffee, fast. Thus, the Keurig brewer just makes good sense.

Soda, while also usually consumed one serving at a time, is almost exclusively enjoyed cold — a problem for the GMCR/KO venture because consumers already have an easy, clean and fast solution to the cold and single-serving problems.

It’s called cans and bottles tucked away in a refrigerator.

Unlike Keurig coffee brewers, the Keurig Cold offers no real advantage compared to the current alternative means of drink-dispensing. Never mind the fact that anytime sugary syrup is mixed with water, a sticky (and sometimes bacteria-laden) mess can ensue, and never mind the fact that the Keurig-blended Coke could cost two to three times as much as, say, a can of Coke would.

2. Soda sales are falling not because soda is inconvenient, but because soda is increasingly seen as unhealthy. Making soda at home doesn’t make it less fattening.

Consumers have spoken: They’re steering away from sugary soft drinks in an effort to reduce caloric intake. In 2012, for the first time in a couple of decades, the average U.S. consumer drank more water than soda, and it wasn’t for convenience reasons.

But the Keurig Cold will do more than just make soda, such as dispense slightly healthier drinks like lemonade or apple juice, right?

Right. Fair enough. But once again, running cold water through a flavoring pod solves a problem that doesn’t exist. Single-serve juices and non-carbonated drinks are already available in a single-serve bottled format and/or easy-to-pour bottles, and it’s dangerously presumptuous to assume a consumer isn’t willing to scoop a spoonful of powdered drink mix into a glass of water and stir it (it’s almost as easy as making a pod-based beverage).

Indeed, many consumers would prefer to mix a gallon of lemonade at a time and keep it handy in the refrigerator. Unlike a pot of coffee, a jug of lemonade is fresh and tasty for days, and it’s bound to be remarkably cheaper on a per-drink basis.

3. The best Coca-Cola can hope for is sales-displacement rather than sales-growth.

Even assuming drawbacks Nos. 1 and 2 can be overcome, there’s still a reason KO stock investors might want to suppress their euphoria.

While GMCR has practically nothing to lose and at least something to gain here, Coca-Cola can’t exactly say the same. See, where any additional sales of the Keurig Cold device and flavor pods will bump up its top line, it’s unlikely Coke will add net sales of soft drinks. Rather, it will simply lead soda drinkers to make their fizzy drinks at home instead of buying them at a grocery store or at a convenience store.

And, in the same sense that Coca-Cola has to compete in grocery stores, Coca-Cola still will have to compete in the Keurig Cold market.

While Coke will only make single-serve pods for the Keurig device, Green Mountain Coffee Roasters is free to add as many competing brands to the ranks of cold-drink pod providers as it wants to. And worse, for KO stock owners as well as GMCR investors, if there’s no patent protection on the design of the pods (a question that’s yet to be answered), that competition will most certainly pop up and chip away at both companies’ Keurig Cold pod business.

Bottom Line

None of this is to say the Keurig Cold device itself is going to be a failure. But, whether it’s due to be a smashing success depends on an investor’s specific definition of “smashing.”

The big question is, are Green Mountain Coffee Roasters and Coca-Cola investment-worthy now because of the partnership? Following the big 26% jump from GMCR stock, no, it’s probably not … at least not for a while.

And as for KO stock, no, the partnership doesn’t make it more appealing to investors, and likely never will.

As of this writing, James Brumley did not hold a position in any of the aforementioned securities.