There will probably never be a manual Genesis sedan ever. None of the other choices came with manual ever either. I think the only Genesis competitor that ever came with a manual was the BMW 5 series.
I'd take a look at one important factor: How will the Genesis drive 15-20 years from now? Resale values? There's a 2011 Genesis sedan 4.6L V8 with 100,000km selling for $19k. A 2008 Lexus GS460 with 100,000km is going for $26k. So good used value with the Genesis.
i don't know if i'd call that an "important" factor. if you buy a car for how it will perform or what value it will have in 15+ years, you are bound, more likely than not, for disappointment. but the car for what it will do over the next 8 years and look at the rest as bonus. people looking for a car for over 15 years really can only look at a very select few if they expect it to be quality the whole time.
an interesting little thing i just did... searched auto trader for cars for sale 1993-1995... 270 in my area... the brands represented more than the others benz - 25, bmw - 11, toyota - 21, honda -18, lexus - 8.... of course, chev -51, ford - 27 were the big guys, but they had a lot more sold originally...
i'm not going to buy based on that, but it does seem to speak for certain brands longevity.