You can find the interview here:
But I will highlight some of the parts which may be of interest to you.
JM= Julian Murphy (the producer)
HC: Is that what you had planned all along?
JM: Pretty much, in all honesty. What we decided to do was to tell the legend how it was in many ways. And I suppose we’re both very sad that Arthur had to die, and that is a massive part of the legend. We tried to sort of soften it and give it a sense of hope that he would one day rise again, and that Merlin even to the present day was waiting for that to happen.
While this doesn't exactly answer any questions in particular, what we can confirm here, is that Merlin most likely did leave Camelot for good as his purpose had been served, and he continued to live on and had to conform to society- he was in exile, and waits, to this very modern day, for Arthur to come back. The producers basically tried to give a sense Arthur would live forever, or should I say, the bromance would, which was really the main focus of the finale. I do think it's equally sad though the idea of Merlin living for hundreds of years waiting for his best friend to rise again. He has become a nobody again (a postman), even more of a nobody than he was back in Camelot. Also you'd think that hundreds of years would make Merlin tired of life or something, but I guess because he is magical he doesn't get sick of waiting!
HC: Also in the finale, we discover that the monarch who will lead Camelot in a golden era of peace is Gwen, not Arthur. Was that a decision that came as the result of Arthur’s death? Or was it something deliberate you’ve been planning for a long time?
JM: It was, actually. We’ve had that in our minds for about three series. We felt that with Gwen, to take Gwen from a servant girl to a powerful and strong queen, a person who can bind the kingdom together, was the journey we wanted to do, and I think Angel delivered that brilliantly. And some of the most moving scenes in that last episode are with Gwen as she realizes who Merlin was, and that the king, the love of her life, is going to die, and that she must then take the kingdom forward. And she plays it in no more than three or four scenes, and that whole story is told. It’s a real credit to her.
Did you just see that? Gwen as she realizes who Merlin was. So that confirms that Merlin's magic was revealed to Gwen. But you know, Gwen was a smart (er) queen as we realised and figured it out for herself- I mean why else would Merlin disappear like that when he has always been 99.9% loyal (the other 0.01% is causing Arthur's death) and Gaius told her she knew the sorcerer and she knew that Merlin was with Arthur. So just some assurance, Gwen was not completely stupid. And we now know what her reaction is. She was overjoyed. I thought it was a touching scene seeing her reaction to it, but very short.
So yeah, read the interview for yourself. I just thought it would be of interest!