There are a lot of other sweeteners that are illegal in the US (not sure in other countries), which are being researched. Whether or not they make it to the population is unknown, but many have much higher sweetness rating than those currently used.
One such product, 'Sweetener 2000' is 10,000 times sweeter than sucrose with NO calories.
Others are cyclamates (being reevaluated); Alitame (2000 X's sweeter); L-sugar form of sucrose and other sugars; neohesperidin dihydrochalcone (1,000times sweeter found in citrus peels such as from naringin of grapefruit and from various flavanoids); glycyrrhizin (from licorice root); miraculin (a glycoprotein from tropical berries); Thaumatin (a protein mixture from a west african fruit...2000 times as sweet as sucrose); there are also others in the polyol varieties, but would have to look them up.
The after taste of these compounds seem to be the negative factors involved as well.
I have not really researched these sweeteners very much yet, so I would not really be able to comment much on them. PubMed here i come...lol. I keep forgetting though
However, as stated earlier, many of these sweeteners are synergistic with one another, and they will increase the sweetness of each other. An example of this is aspartame and saccharin and aspartame/acesulfame-k.
I think one of the main reasons that certain beverage companies choose one sweetener over the other is not only for their stability, but also because of their mouth texture benefits...ie sucralose.
BMJ