Isn't that Marvel NOW Thor, who already lost to the Sentry? :-7
Or do you specifically have the regular Sentry / Void in mind, without the Death Seed amp? Might be a good fight, but Sentry has a ridiculous speed advantage over Thor, so there is that.
And then there is the question about the scale of Sentry's amp through the Death Seed. He is not the only Horseman of Death... there are also Banshee, Daken and the Reaper and all of them didn't look THAT powerful and impressive in their fights against the Uncanny Avengers. I would argue that the Death Seed amp isn't even that high for all of them and that they still can be defeated, if someone matches their power level - which no one does, when it comes to the Sentry, especially now without the Void ... if Rick Remender has done his homework he knows how powerful the Sentry now actually should be ... him not having to deal with the Void and being in control of his power set makes him more powerful than the actual Death Seed does.
Just my two cents.