It appears Metro Redux, the recently-announced re-release collection that brings Metro 2033 and Metro: Last Light into the world of next-gen, will make use of its "director's cut" description. The graphics have been gussied up to accomodate next-gen hardware, but developer 4A Games reportedly took a full dev-cycle year to go back and retune everything for the best Metro experience.
For instance, Metro 2033 had an episodic feel, jumping around from one location to the next with only a page of text to explain the story's movement from location to location – now these gaps have been bridged with interstitial moments of gameplay that make the overall game feel more cohesive (not to mention the game has been re-created with the next-gen ready Last Light engine).
Cohesion was a big problem, arguably, with Last Light, which felt like it was trying to be too much of a typified shooter compared to the original game's slow, brooding horror atmosphere. This too has been addressed – now you can play both 2033 and Last Light in modes designed to whatever experience you prefer.
To wit: survival mode features a more horror-style pacing and tone closer to the original game, including weapons rebalancing and ammo, slower reloading and other adjustments. On the other hand, if you preferred the faster pace of Last Light, you can play either game in Spartan mode, which has its own set of design and pacing tweaks.
If Last Light has truly been retooled for to play like the original 2033, it'll be worth picking up the Metro Redux set, though even playing 2033 with the Last Light engine is pretty tempting. Jury's still out on how it's all going to shake out, but this is potentially great news for Metro fans.