There seems to be a cycle. Recently the democrats have had the popularity and numbers. It seems to be a toss-up now. I will say the next elections the GOP will win the presidency and gain more House and Senate seats. By the 2020's I predict the democrats to have the numbers advantage by the middle part of the decade.
In 2014 the House and Senate will remain unchanged, except for the amount of tea party members will decrease. In 2016 it is very likely that a democrat will win the White House, Clinton seems most likely. Going beyond that is to hard to calculate. Once the ACA settles in and people begin to realize that it's not the "boogeyman" that the republicans have been trying to make it, this will turn most Americans against them, even more so than today. How much damage the GOP receives, and for how long, is entirely up to the GOP. If they remain nothing but the party of no! that they are today or move farther to the right, they run the risk of disappearing into history. Should they be able to silence the more radical elements within their caucus, and once again learn how to compromise, the damage will be less. But until they can develop a message of optimism and ANY plan, at all, to improve the lives of the average American, they will remain a minority party for many more election cycles.
I would say it is a fifty-fifty chance. The GOP has the lower approval rating but their rating has been in the sewers for awhile. The democrats and Obama himself are taking a huge hit in their approval rating. Contrary to belief the more people find out about the ACA the less popular it and the democrats are.
Nobody will dominate because both parties have flaws and need to have checks and balances. Republicans act as restraint on Democrats and Democrats nag Republicans. Without both parties, America tilts left or right, and we all know what happens when a ship tilts too far one side or another!