Is it worth waiting?

I applied for an internal job in January, interviewed the same month and after 5 weeks I had the second interview with the same hiring manager. He said he likes me a couple of times and I was 90% sure I would get the job. The following Monday, I received an automated rejection email. I wrote to the hiring manager thanking him for the time and opportunity and I am still hoping we could work together in the future. Also politely mentioned to keep me in mind if there will be an opening in his team. He responded and said I did well and he’ll let me know if they will open another position. Is sincere or just being polite? I really want to join his team and last year they opened 3 positions and I hope they will open one again soon. I’m asking because I am up for promotion in my department and if I accept it I would need to stay in the role for a year which will prevent me from applying to another department. Btw, the job position is 3 levels up from my current ranking.