The GTA V Era Los Santos is goning to be WAY bigger than the GTA IV Era Liberty City. However, you must remember, Los Santos is a city, not a state. If Rockstar is making Los Sanots a city instead of a state, it would definitely be smaller than San Andreas.
Also, I highly doubt CJ will appear in GTA V. He would be too old by then. Also, GTA V would most likely be a reboot of the GTA series, so if that was the case, CJ wouldn't exist in the new timeline.
There is nothing wrong with DLCs, except for the fact that they have less missions, and possibly less features. Just think of it as a different video game of the same series.
And dude, please don't swear. It ain't cool to do so.