But first, let's take a step back in time just like what will be done in this summer's big X-Men sequel to look at something The Daily SuperHero wrote last summer after The Wolverine was released in the theater. The bonus scene at the end was done to set up X-Men Days of Future Past and perhaps more.
In that scene there was a quick glimpse of a white-ish robot hand and I put the theory online that Nimrod could be a part of X-Men Days of Future Past. Now with the release of what the future Sentinel looks like, there's still a chance Nimrod could be that future version of a Sentinel.
To recap a little bit about Nimrod, in the comics he is an alternate reality version of a mutant hunting Sentinel robot but he's also more advanced. Nimrod is virtually indestrucible since he can regenerate himself and in the new image of a future Sentinel, it seems like the future Sentinel is made of technology which could regenerate as well. This would definitely be a reason for Wolverine to go back in time to stop the creation of the tech by Trask Industries which eventually leads to the future Sentinel.
While all of this is based on just a logical theory and gut feeling, there's a strong chance it could be right. Nimrod, despite his silly name, is a force to reckon with in the comics universe and an adapted film version would be a similar threat to both mutantkind and mankind.
UPDATE: Here's a bit of information about the future Sentinel per the designer John Myhre (via Empire Magazine.)
"They're biomechanical weapons. We had to come up with what would be the ultimate version that could actually, in principle, stop the X-Men. We started with this idea that they were almost made up of magnetic plates slapped over one another, imagining that the plates could contract or grow, so the Sentinel can be skinny to get through a small space or the plates can open up to become a bigger shape. So they have become virtually unstoppable."