It wouldn't be all that hard to do an X-men: Days of Future Past without giant robotic Sentinels, but it would be hella disappointing. Probably so much that Fox would never even consider leaving them out, despite the cost of putting them in. Mark Millar, the talkative comic book scribe who also serves as a creative consultant on Fox's Marvel flicks, puts any doubt to rest in an interview with SFX, saying the Sentinels will be in there and causing havoc...
Millar: "I don’t really want to give too much away but the Sentinels are a big feature of this story. They will be cool and this will deliver on all of the teasers. We’ve all been waiting for this ever since X-Men: The Last Stand showed us one of their heads. Now it is finally coming, and we only have to pay ten quid to see it in the cinema."
He also goes on to talk about the large ensemble of returning faces, comparing it to J.J. Abrams' Star Trek. One name in particular he mentioned was the return of Ellen Page, who plays Kitty "Shadowcat" Pryde, an integral piece in the Chris Claremont comic. It's unclear if she'll be quite as important in the film, but Millar seems to think so....
Millar: "Kitty Pride fans will not be disappointed."

Millar: "Kick-Ass 3 is going to be the last one though. I told Universal this and they asked me, ‘What does that mean?’ I said, ‘It means that this is where it all ends.’ They said, ‘Do they all die at the end?’ I said, ‘Maybe’ – because this is a realistic superhero story. And if someone doesn’t have a bullet proof vest like Superman and doesn’t have Batman’s millions then eventually he is going turn around the wrong corner and get his head kicked in or get shot in the face [laughs]. So Kick-Ass needs to reflect that. There has to be something dramatic at the end, he cannot do this for the rest of his life.”
Makes sense to me. I can see Kick-Ass getting offed in some random fashion like Omar from The Wire.
Kick-Ass 2 opens on June 28th, X-men: Days of Future Past on July 18th 2014.