Hi Sibtain,
Portugal and The Netherlands are the two countries in the world with the most OutSystems developers.
So yes I would like to think you have good career opportunities as an OutSystems developer.
The nice part of OutSystems is that you can learn it for free on outsystems.com/learn, and certify yourself as an OutSystems developer (not for free).
I started my OutSystems career when I was already way in my 40s, age should not be the limit if you have an extensive career in IT. It all depends how easy you can learn and adopt to the OutSystems way of software development. Salary wise of course it can be a challenge especially if you have already many years of experience in other IT technology, and start from zero 0 with OutSystems.
Regards,
Daniel