Polls show this and next Tuesday as being a bloodbath for the Sanders campaign.
The primaries scattered throughout May aren't really significant enough to make a difference and might very well be a wash anyway.
The next important primary date after 4/26 is 6/7 when California (and to a lesser extent, New Jersey) votes. Expect to see a lot of memes along the lines of "Bernie is down 400 delegates? Ha, California alone has over 500!" while ignoring that Hillary would need to completely crater below the viability threshold (the point at which a candidate is awarded any delegates) in order for Bernie to win enough delegates to make up the difference. That also ignores that Hillary won Cali in 2008 (and has been remarkably consistent in holding onto states she won then, the only exceptions I believe are New Hampshire and Vermont) as well as the fact that the polls have her leading there, although that could change.
Basically - the notion that Bernie could overtake Hillary in pledged delegates, or even come all that close is wildly fanciful. Hillary has something like a 57/43 lead in the popular vote right now. For all the whining about superdelegates being undemocratic and overturning the will of the people, Bernie is the only candidate who's stuck making excuses for why the supers should side with him anyway.