I think the ending will be dramatic.
The BO has their motive and goal in the story. The story will end when BO has found the way for their goal to come true. As for what is their motive I believe it lies with Vermouth since she is the boss's favourite.
We can see that the lady has not aged since very long time ago. It could be that the boss is looking for some miracle cure or miracle drug that can reverse time. And Vermouth may be the "Only" successful experiment?
So lets presume the boss is looking for a drug which can stop time. Then everyone, Mouri, Ran, detective kids, Heiji, his parents, everyone became involved and dangerous things occured. In the process, they realise Shinichi is alive and Haibara's whereabouts, know the truth about the shrinking. They want to either kill them or make use of them for the goal and thus captured everyone that has to do with them. And so, everyone knows shinichi's secret. Probably he will have to work with Heiji, Haibara and his parents to rescue everyone from the Black organisation and capture the head.
When everything ends, Conan will faint out of exhaustion and end up in the hospital. He will wake up finding Prof Agasa, Ran, Heiji, Mouri, the kids, and his parents beside him and everyone knows the truth then.
His mother will first cry and give his Shin-chan a hug... Conan will then complain.. Then suddenly when he realises the others are there and there will be awkwardness.
Then heiji will start the ball rolling by greeting Kudou openly. Then ayumi will say... Conan kun... no... Shinichi san... then Conan will stop them and say, its ok.. .just call him like they used to ... then Haibara will make a joke out of it and ayumi and the rest will break out with a smile.
When everything seemed not so heavy, Mouri will most likely start to complain about Conan ... and Heiji will add in saying that his deductions are all from Conan and Mouri will shut up with an embarassed face. Then everyone will start laughing and when everything gets all lively, eveyone will realise the scary aura coming from Ran who has kept quite for very long.
So, everyone decides to leave the room for the both of them. This time, Conan will now tell Ran everything...that he was all along by her side and how difficult it was to see her cry and not tell her anything about it. Ran will cry and scold him stupid and give him a hug. She might say she already have a slight suspicion on that and that he was stupid to have carried all of that. Maybe Ran will then give our little Conan a kiss despite his size XD Then she will tell him how much she misses him and how she feels. Conan will reply that he too felt the same way... but then proceed to tell Ran to give up because he is still in his child form. He might not know when he can turn back.
Ran will then say she doesnt mind and will wait for him no matter what XD
I guess that should be touching enough. XD