Trump's been leading the Republican polls for some time, though he still has a pretty small overall share and Carson has been surging recently. Its pretty hard to justify a claim that its clearly heading toward any particular winner on that side (particularly since its not decided in a national election, but state-by-state elections to assign delegates in a manner which isn't proportionate to share of vote, and there's not frequent enough state-by-state polling to have a clear picture of even the current state of those, much less where they are likely to be by the times they are held.)

On the other hand, while Sanders is doing well in some places, Clinton's still got a about a 20 percentage point lead in most national polling; she's hardly "imploded" the way Bush, widely perceived as an early Republican frontrunner, has. Many of the same concerns exist as discussed above with the Republican ticket as far as drawing conclusions go, but what you can read from polls doesn't show anything like a clear course to a Sanders win.