In the trailer for The Last Jedi released on October 9, 2017, we see what seems to be a new upgrade on a Resistance X-Wing - a large, central thruster of some sort, mounted right behind the hyperdrive.
As the thruster fires, it seems like the X-Wing matches Poe's from the previous movie. At least, it seems dark in color, with orange markings.
The scene then cuts to a close-up of Poe's eyes as he flies, further implying that this is his X-Wing. However, I don't recall seeing a thruster on his X-Wing in this position in The Force Awakens - or, for that matter, on any X-Wing variant in the past.
This may not be answerable yet - and there evidently wasn't a lot of information about it last time around. But has this been covered in any other supplementary materials? For instance, did his X-Wing get a tune-up post-Force Awakens in any of the comic books or novels?
Or do we need to wait for the new Incredible Cross-Sections book? :)