** LAS VENTURAS SPOILERS, BIG TIME. READ @ OWN RISK **
When you reach the last mission, choose option A. When you sadly finish the mission, switch to Michael and go to your house. Keep going to your house until Tracy is there on the staircase giving you $50.
If you haven't completed the Eplison Program Quest (all 8/8, last mission 100% completed), do so now. When finished with these missions, call Franklin to hangout.
Take any car and travel to Sandy Shores, where Trevor's trailer is. Approach Ron and Wade (who are standing by the door, drinking beer) and pull out a large gun. At this point, you are able to kill Ron and Wade so do that.
The side mission 'The Lost and Damned Again' will start and an onslaughter of Sandy Shores residents working under Trevor will come and attack you with heavy machinery. Do not let Michael or Franklin die otherwise the side mission will cancel and since this is a large easter egg, you must start from the point where you give Tracy $50 in order to replay it.
When finished, two unknown The Lost MC bikers will approach you. They will talk about a new plan to 'start up in East San Andreas' and the revival of The Lost MC. They talk about casinos, mafias, drugs, strippers, weapons and obviously hint Las Venturas. When the cutscene ends, you make THE final decision of the game:
Travel to Las Venturas for a while or stay in South San Andreas?
If you say 'Yes', Franklin will volunteer (with Lamar) to travel to Las Venturas with the Lost MC members and Franklin becomes an unusable character for 2 in-game weeks.
Around 2 in game weeks later, Michael will receive a call from Franklin. He'll mention that "sh*t is going down here in LV" and "some Angel of Death niggas here to crap on our business, yo." This is the part where you travel to Las Venturas. Michael will be asked to drive to LS Airport and will have a cutscene of him traveling across the water in a FlyUS plane, landing at the LV airport.
When the plane lands, a video is shown of Michael meeting Franklin and Lamar at the airport and they travel in a Primo to the hideout. You start to drive the Primo along a designated route but DO NOT and i say DO NOT explore Las Venturas at this point. Drive to the destination and you'll see the AoD covering the entire TLAD new clubhouse. Kill everyone there (including TLAD members) and clear out the place hollow.
At this point, you are FREE to travel across the SMALL city of LV (yes, it's a lot less smaller than LS) but the town is mostly a wasteland. There's nothing to do and you only get to explore a good game day (24 min) before the final choice begins.
This mission starts as Michael. Run up to the marker and a cutscene shows Franklin discussing with Lamar about their big plans in Las Venturas. Michael says he must return home to his family and attempts to persuade Franklin and Lamar to come with him but Franklin, with his huge cut from the [CENSORED] heist, attempts to bribe Michael with even more cash to get his family to move here.
Michael immediately denies and mentions how HE was the one who raised Franklin to be a professional. With all of his money, Franklin becomes greedy and trash talks Michael at that point, with Lamar trying to stop Franklin but Lamar's efforts are worthless. The final confrontation between Franklin and Michael happens.
You are switched to Michael at that point. Franklin runs up to the top of his new building while Michael holds a gun up to Lamar's head. Lamar decided to side with Michael as he says "Man, he used to be my short nigga. But you is more black then he is" (was LOL) and you chase down Franklin until he is cornered on top of the Caratta Estate. You are told to push Franklin off the roof but if you walk away, Michael will sigh and not say anything. He'll calmly take the elevator to the top of the building (Lamar following him, questioning his moves) and leave.
Michael takes Franklin's Primo and drives to the airport, calling Amanda saying he is returning. Dave calls asking where you were to which Michael replies (if killed Franklin) "My true son is dead." If Franklin is spared, he will reply "It's over. Both of em, gone. I guess it's back to square 1 in the sun."
Michael is the only playable character from there on out. Franklin will occasionally email you if spared but it is mostly junk to which Michael responds positively to. Las Venturas (like North Yankton) is unavailable.
Took me 7 minutes to write this guide on how to get to LV, hope you enjoy!
TL;DR - Lost MC and AoD are gone for good in the desert regions of South and East San Andreas.
Las Venturas is not as big as it is in real life, it is about the side of Los Santos but very poorly detailed.
The TRADE-OFF of going to LV is loosing TWO of the main protagonists!