It’s not unprecedented for a network to give a series a very long midseason break, and it’s a possibility for Criminal Minds.
Still, I’d put my money on Criminal Minds premiering its second half of Season 14 in early January and then ending its run whenever it runs out of episodes.
A second direction that is likely less appealing to fans is for CBS to hold off on debuting the second half of Season 14 and simply premiere it later in 2019, allowing it to come to an end in late April or May, as usual.