Here’s what I think but part’s of it are still not entirely clear to me.
For some reason Rumple has recognized that Snow’s and James’ love is so powerful that even curses and potions can’t permanantly destroy it. For example, after giving Snow the “forgetting” potion he tells Grumpy that nothing can make her the way she used to be again and there isn’t a potion that can make her fall back in love with James. But then he gives her the bow and arrow and tells her that it never misses it’s target. It obviously wasn’t meant for the EQ then because the arrow hit James. She didn’t need a potion to make her fall back in love with James. Even though she couldn’t remember him, she fell in love with him all over again. Rumple obviously knew that their love is so strong that as long as he could get the two of them together again in the right circumstances they would kiss and Snow would then remember him without a potion.
Even though Rumple has now been described as the most powerful man in the world, two things still seemed to have escaped his power – love and life. And in this episode he made the comment “If you can bottle love you can do anything.” I think the two most important people to Rumple have been Bae and Belle and, at least so far, it seems that he believes that they are both dead. He made the comment to James’ father the King that once someone is dead you can’t bring them back – but that was before he had the ability to bottle love – “If you can bottle love you can do anything.” I think that now that he has found a way to bottle love, he is one step closer to finding a way to bring back the dead – which would usually be a very dark process and require the Darkest Curse imagineable, unless you also have the ability to bottle love and use the product of the strongest love that exists (Emma) to destroy the Dark Curse. I found it interesting that when he added James’ hair to Snow’s in the bottle it looked like a DNA helix – which would mean it was Emma’s DNA.