Yes they will return at some point...as will captain marvel, psylocke, captain britain etc.... creators run out of stories to tell and these characters end up becoming plot devices instead of characters, so they appear and disappear until something good or the lack there of starts cooking..
NOTE : someone might want to put the "i" in "Will" in the thread title.
I really do the think the purpose of the Sentinels are to be plot devices. Here are colossal robots, hunting and killing mutants for the people that fear them. Where is the character in that for these Sentinels? These guys are merely puppets to characterize the human race as scum.