The dems have a major problem. Ever since 2008, the GOP with Rove, paid about $30 million to have a software developed that can be used to re-draw the district lines in all of the states based on the demographics. voting preferences, and personal preferences, in each area. They've been doing this ever since and it played a major part of the 2010 mid-term elections (that and due to the Dem voters being allergic to mid-terms.) Because of this, there aren't enough dems in many of the state districts in say, Pennsylvania for example, to defeat an incumbent US House rep in the district. This means that for at least until 2030 or longer, the GOP will control the house. (I do not think that I will see the dems controlling the house again during the rest of my lifetime.) This means that no matter who the Dem President is in 2020 (more on that later), it will be incredibly difficult for that President to get anything done. Additionally, the Senate dems will likely have 23 seats up for re-election in 2020. Since it's a mid-term election and the dems don't come out to vote, the GOP probably will take more seats back from the Dems. 2020 will be the next time in which the Dems have a chance to regain some seats but this will only happen if the dems have found a candidate that the Black voters support at the same volume as they did for Obama. Without this, there will be no dem President (see 2016 election results). Pence will win re-election (or Trump if he actually sticks it out for the full 4 years.) The coattails for the 2020 Dem candidate have to be long to take back many Senate seats and it will likely only be in bluish states. Regardless of how the dem Pres candidate does in 2020, he/she won't be able to help the dems take back many or any house seats due to programmatic gerrymandering by the GOP mentioned at the beginning of this post. If the latino population continues to grow in this country, some states could flip to dems for the President and Senate (see Arizona which Clinton won in 1996 by ~32000 votes and prior to that no dem has won since Truman won it in 1948), however, it will take another generation before there is any major change in demographics of many of the key states. I do not expect to see anything major within the rest of my lifetime.
Personally, I want to see more moderate Republicans, like McCain, that I can support. The Red States will automatically support the candidate regardless of the person's politics (see Trump), and independents will likely vote for. However, the tea party nuts have been trying hard to defeat any moderates.