So much to say on this one. Where to start?
A common thought seems to be of Ran being given the APTX. I am absolutely against this! I am up to episode 400, and thus far (as I recall) Conan and Haibara are the only victims we've SEEN of the drug. I must emphasize SEEN, as Haibara made it clear when she arrived that the two of them were the only humans to have survived it. We have no way of knowing just how many people the Black Organization has used APTX on, but we know that it has KILLED every one of them besides Conan and Haibara. Therefore, if Ran is given the drug, the odds are that it will kill her as well. I don't even want to face the chance of this happening. (And, conversely, if Ran is given the drug and DOES revert to a child form, that would make it a lot harder to believe this drug was so dangerous/deadly as to kill EVERYONE the Organization poisoned with it aside from Shinichi.) So please, no APTX for Ran!
Next, should she even find out the truth at all? Well, I agree with the assertion that if the show just keeps doing the same thing over and over it will get stagnant. I also agree that Ran learning Conan's secret would change the tone of much of the series. Putting those two things together, I think Ran's discovery might revitalize the series and allow it to go further. It would allow for a few episodes (say 10-20) of awkwardness between them as she grows accustomed to the idea that the child who has been looking out for her for who knows how long is actually the man she loves. Then there could be plenty more episodes following that as she actively helps him preserve his secret, perhaps distracting people as he puts Kogoro to sleep to present his deductions and even learning from him to aide in those deductions. In short, working from the sidelines rather than watching obliviously. So yes, I think it should happen.
The question then becomes WHEN should Ran find out that Conan is Shinich? I think this should happen somewhere after episode 1,000 (probably on episode 1,001), letting that be the line of demarcation. As for the circumstances, I imagine Ran being in some kind of danger involving the Black Organization (though not necessarily the Organization's endgame), and Conan is put in the situation where either the knowledge of his identity will somehow save Ran, or where saving her will somehow reveal his identity to her. From a storytelling standpoint, this would be the best way to present the reveal for its dramatic tension and intensity. This would also allow Conan, after the resolution of that conflict, to adequately demonstrate the threat posed by the Organization so as to somewhat quell Ran's anger at being deceived for so long.
Finally, Ran's reaction to the revelation. In short, she will be LIVID. But, I think it will be fairly easy for Shinichi/Conan to defuse her rage, especially if the reveal is handled like I have already said. The demonstrable danger of the Black Organization should partly calm her, assuming Conan gives the FULL explanation following the incident that led to the reveal. I believe that he could then completely defuse the rest of her anger with four words. "I love you, Ran." I think the shock of hearing these words from him for the first time would take the wind out of her sails, no matter how many times Conan has seen her naked, slept with her, or whatever; all of that would leave her mind entirely in the wake of an honest, heartfelt confession. And I believe that he would do it, too. I honestly believe he was going to tell her he loved her in the restaurant where his father proposed to his mother, but he reverted back to Conan before he had the chance.
I have always been in favor of Shinichi/Ran in the real continuity (even though the fanfic series I'm writing on is a Conan/Ayumi fic), so that is how I hope things will come to pass. What do you guys think of these ideas?