The Allspark could make a return to the Transformers live action franchise in Transformers 4, according to NPR. My assumption is that if this rumor is true, the Cube would return as some sort of flashback. TFW2005's summary of what was talked about on the radio station is below:
"Randall Thropp, a Paramount archivist, recoils in mock fear from the power
of the AllSpark as set decorator Rosemary Brandenburg takes it from the glass
case. The AllSpark was used as a prop in Transformers; it may have another life
in an upcoming sequel."
A little movie factoid: The AllSpark Cube
was technically a prop in the first Transformers, because an actor actually
touched and even ran with it. Brandenburg thinks the cube might make a
reappearance in Transformers 4 as set decoration. It's too early to tell. But
archivist Randall Thropp says that unfortunately, she can't take the AllSpark
and use it in the film.
"That is the only cube we have, right here,"
Thropp says. It resides in a glass showcase.
Brandenburg can borrow the
cube and make copies, though. "A movie set is a pretty dangerous place for
things," she says. "We have to repair things constantly. Our special-effects
brothers and sisters are running around blowing things up, and our stunt
brothers and sisters, too."
Brandenburg often has to make multiple copies
of items because of all those blowups.