Sanders is currently beating Trump 49.7% to 40% in polls.[1] Admittedly it is a long way to November, but with all the stuff Trump has said and done, the campaign against him practically writes itself. He has his own party calling him a liberal democrat while there's an endless number of clips of his incessantly racist, sexist, jingoist comments, on top of zero experience in government and four past bankruptcies. Cruz I'm less sure about (Sanders still has 3% lead, and 5.3% over Bush, -1% to Rubio), but I'll gladly take that even money bet if it ends up being Trump vs. Sanders. :)
A far worse scenario is that it ends up being Sanders vs. Trump vs. Bloomberg, Bloomberg siphons disproportionately more votes away from Sanders, and we do end up with a President Trump - plus Republicans retain control of Congress and Trump gets to appoint the next SCOTUS justice. A Trump presidency with control of all three branches of government would be scary indeed.
[1] http://www.realclearpolitics.com/epolls/2016/president/us/ge...