There is still no official confirmation as of today, but you can bet that a new Ice Age movie sequel is being planned by Blue Sky Studios and 20th Century Fox. And actually some plot details of Ice Age 4 may have already leaked online!
Ain't It Cool News manage to get their hands not only on what could be the premise of Ice Age 4, but also on a possible title! According to them Ice Age 4 would be titled Ice Th4w, a pun on Ice Age Thaw and Ice Age 4, and here's the plot:
"[...] it seems a fourth Ice Age film has been well underway or the past few months. A friend of mine says the 4th installment sees Manny, Sid, Diego, Ellie and Scrat frozen solid and accidentally defrosted in a museum in present day.
At this stage the film is being called 'Ice Age Th4w'."
AICN
I've mixed feeling about this plot of Ice Age 4... It would probably make for a really funny movie, and I can definitely imagine Scrat the squirrel going nuts for hazel praline chocolate. But I would be sad if our friends from the Ice Age were stuck in our time... I hope that thanks to some plot twist our furry heroes would manage to go back in time and avoid their4 frozen fate. Maybe thanks to some alien time travel machine? It wouldn't be so far fetched, we did see a UFO in the first film after all!
Besides they definitely need to go back to the Ice Age so the franchise can continue! And you can't separate the young Peach from her father!
So please, do bring Ice Age 4, but if the plot above is real, I beg you to allow our friend to go back in time to the Ice Age with their families.
:)