@ Brotha...I agree with your assumption about R* not going to over-do the number title, R* does not do silly stuff like GTA - 122
there fore I beleif the next *Big* game will have a name, examples:
1) VC you mentioned, maybe R* is not satisfied(like in III's LC)
2) LS many fans loved that area, and wanted it better.
3) SF the same with this gta city
4) LV to a lesser degree
5) last , but not least the mystical * Carcer City * which is a logical choice, because, R* don't have to follow any current city-scapes on this one, its made-up, R* is totally free here to design a gta city to its creative mind, which the sky is the limit.
Note: DLC has me stumped as to how it will fit in, prob. like you say, to tide us over between *Big* games.
You have got a good handle on this whole thing, I hope you are correct, your idea's on this are most desirable,because they fit the gta model we've grown to love.