One thing you have to bear in mind is that orchids are very slow growing plants so not seeing any significant growth in 4 weeks is not necessarily a cause for concern.
It certainly looks healthy in the flask so I wouldn't be in a hurry to deflask it until it is bigger as it will then be stronger and have a better chance of survival.
However it all becomes a judgment call and it would probably be fine to deflask it now as well. It all comes down to experience and you only gain experience by taking decisions and seeing what happens.
Good luck with your deflasking.