No, in my opinion Missouri represents the past. They need to focus on the future. The future is: Nevada, Colorado, New Mexico, Arizona, Virginia, Florida. As Obama proved, you can push trends along a little faster with the right outreach. They should work on building the groundwork to make states like Arizona and Colorado regular democratic states, rather than focusing energy on winning Missouri for perhaps the last time in a generation.
I personally think the Democrats are likely to win in 2016 so I'd rather they build momentum for 2020 in states they might ultimately lose in 2016 rather than win a few more electoral votes.
If the Democrats win a third consecutive cycle in 2016, and with Hillary Clinton emerging with a higher popular-vote margin than the re-elected 2012 one by President Barack Obama, then one should look to the lowest-ranked states (of a total 24) from the losing 2012 Republican column of Mitt Romney.
20. Indiana (Republican pickup), R+10.20
21. Missouri, R+9.36
22. Arizona, R+9.04
23. Georgia, R+7.80
24. North Carolina (Republican pickup), R+2.04
Nebraska's 2nd Congressional District was also a 2012 Republican pickup, by a margin of just over 7 percentage points, and carries similarly to Indiana. (They had tighter margin spreads from Elections 2004 and 2008.)
I would not write off Missouri and/or Indiana from the Democratic Party's potential. We're in a period where the percentage of states being carried in winning presidential elections is underperforming the historical average. We're overdue for a landslide in the Electoral College. And why shouldn't that be viewed as an opportunity, given realigning periods, for the in-party?