Somewhat. Lemmix and NeoLemmix do support RGB-based graphic sets and VGASPECs, and from the next release, NeoLemmix will also support RGB-based MAIN.DAT files, which essentially means all in-game graphics will (or at least can) be RGB-based.
However, there are three reasons why that may not quite be adequate for back-porting the graphics from PS3 / Vita versions:
1) Although they support RGB, it's not full 24-bit color. It's only 18-bit; essentially this means it's still limited to the same color pool as the DOS games were, it's just not limited in how many of them at one time can be used.
2) Most likely, the PS3 / Vita (and even PS2 / PSP) sprites make use of alpha blending. (Neo)Lemmix doesn't support this; alpha is limited to "transparent pixel" or "solid pixel" in these, there's no inbetween.
3) The biggest one of all is resolution, or in less-technical terms, how many pixels are on the screen at a time. Although (Neo)Lemmix does zoom to nearly fill the screen, internally the graphics are still a 320x200 resolution, just like the DOS games. Even many other clones don't do much better than this; Cheapo was 320x240. Lemmini and SuperLemmini can display more area at once due to being in resizable windows, but effectively function at a 640x360 resolution (not including the skill bar, unlike the others which *is* including it) - it's somewhat hard to directly compare them. I'm not sure where Lix stands, but it's probably similar to (Super)Lemmini. By comparison, the minimum resolution that's usually considered "HD" is 1280x720, or a non-widescreen equivalent would be 960x720 (meaning that you could fit 9 copies of a NeoLemmix screen on a non-widescreen HD screen space, with full detail, and still have a strip of 60 pixels each above and below to spare). Since "HD" usually also implies widescreen, that'd also have to be taken into account. To put this as simply as possible; without resizing (and thus losing some detail), a PS3 / Vita lemming is most likely about 3 times the size of a (Neo)Lemmix one.
I don't really plan on expanding NeoLemmix beyond those; it'd involve reworking so much of the core elements that it'd probably be more effective to create a new clone from scratch for this purpose. Which I'm not saying I'd never consider, but it's not on my todo list any time soon; chances are if I feel like creating something from scratch, it'll probably be a completely original game (and most likely not an IRS).