I think of course Marius would invite them to his wedding... But Marius really by a miracle avoided death because of treason and his grandfather probably wouldn't support his friendship with Enjolras and Gavroche. It's really hard to say what would happen later.

Do you have other ideas?

Okay i see that. What about them meeting Valjean at the convent, meeting Cosette and comforting her after Valjean passes?

They would probably become friends, I think. But I'm really convinced that Enjolras would be executed - in the book it was one moment, in which king's people were looking for revolutionists.

What's your opinion? Do you have any other theories?

My theory is this, Madame LennonBaggins:

Grantaire takes the shot meant to kill Gavroche and as the barricade falls, Enjolras and Gavroche escape into the sewers with Valjean and Marius. The trio mourns the loss of the barricade, but Cosette arrives and meets Enjolras and Gavroche. After Marius speaks with Valjean, Enjolras and Gavroche attend the wedding. At the convent, the three boys and Cosette meet Valjean and thank him for saving Marius. And as the spirit of Fantine appears to bring Valjean to heaven, Marius and Gavroche comfort Cosette, while Enjolras thinks of restarting the revolution.

What is your theory?

I'm a lady!

Your theory is very possible, I think... But it's hard to say what could really happen...

Gavroche would probably be adopted by Marius, but Enjolras would be exucted for treason. 

No, he wouldn't have been executed for treason.  None of the real life rebels from the real barricades in June 1832 were executed nor were they charged with treason.  I am not sure what they were charged with, it may have been insurrection, I am still researching this.  A small number were sentenced to death, but they were all commuted to imprisonment on appeal.  They had good criminal defence lawyers then in France already. It seems a lot of the lawyers were republicans, as both they and the defendants made political speeches in court. 

AND in May 1837, five years later, King Louis-Philipe, the king they were fighting against and trying to unseat, gave them a Royal Amnesty!!  Did he really think that by releasing them from jail, that they would stop fighting for a Republic?  They continued agitating while in jail.  Well, in 1848 the rebellion was successful and he lost his throne and fled to England where he stayed until his death.

Enjolras wouldn't have left a falling barricade.. he would probably have to have been wounded and unconscious to stop fighting. Grantaire wouldn't have died if Enjolras didn't. Gavroche might have been able to return to the barricade without getting shot.

Enjolras would wake up in prison next to Gavroche and Grantaire. He would have then blamed Gavroche, Grantaire and himself for living when their friends have all died. When he realizes that Marius is living a happy life with Cosette, he would feel as if they have betrayed the cause. He would continue to rally up the people, even in prison.

Gavroche would feel terrible in prison because he would be worried for his boys... However, he would try to make the best of prison and make it out to be just one huge joke. He would laugh in the face of failure and prank all the guards. He would probably also plan to break them out of prison.

Grantaire would be drunk. And he would say he saw it coming all along. Which will make Enjolras really upset.

They would all mourn for the deaths of their friends. Enjolras would either fall into depression or join the rebellion that overthrew Louis-Philipe... Grantaire will do whatever Enjolras chose to do... Gavroche would continue to be Gavroche... 

So yeah... that's what I think would happen?

You don't think that Gavroche would have fought at the 1848 barricades?  In the novel, he says he fought in the 1830 revolution.  He was asking Enjolras for a musket and says he had one in 1830.  He would have been about 9 then.  Republican revolutionary from a young age.  Fought in 1830, 1832, probably be one of the leaders in 1848.

I forgot to mention that in prisons in France in those days, there were different sections for ordinary criminals and political prisoners.  Political prisoners had better conditions.  The rebels were jailed as political prisoners.  The Royal Amnesty in May 1837 was for all political prisoners.