One should never say never when it comes to forecasting the outcome of an election two years in advance. But it might take a major scandal in the Republican party, or for Republicans to splinter into factions, for Democrats to have more than a remote chance of winning the House.
And there is one more factor working against Democrats: they have become increasingly reliant upon voters, like Hispanics and those under the age of 30, who do not turn out reliably in midterm election years. Democrats have a broader coalition than Republicans do in high-turnout environments, so perhaps this will benefit them in 2016. But these are not the voters you would want to depend upon to make gains in midterm election years, when turnout is much lower.