What do you think? Should we study/work abroad for a year or so in order to develop ourselves?

We can choose wherever the place we can study or work as far as financial and family situation allow us. I think more important for us is to determine our mind to be a part of the world or stay in domestic. When we be a part of the world, even staying in Vietnam, we have lots of chances to communicate with the people from all over the world.

I share a small point of view.
I have the same opinion with Ms. Rosie Vu, there are many majors that you can study in Vietnam for a good results (instead of you want to study in depth in some rare specialized majors)
I graduated from a small school (Binh Duong College), major in Office Secretary. Very normal! But now I work for big firm and try to be professional. It's self-study!

What do you want to develop:
Just as an example,
if you want to develop in sales and tricky situation: corruption, kickback, all sorts of competition trick (fake, no guarantee, untaxed import...) there is no better place than Vietnam to learn.
If you want to develop medical skills France excellent value for money (free university),
IT is California, Finance London or New York, sustainable development and NGO charity VN or Laos is OK...
"those who go with the wind have the destiny of a dead leave"

Vietnam is developing in every way. Things that need improvement are (not limited to)
* Professional Management (eg. As a Manager, shouting at your staff died with the dinosaurs, but I see it happening too often here)
* Professional Customer Service
* Taking Professional Responsibility (eg: a director who needs to pass around a decision to several different people before making a consensus decision is not taking responsibility for their role). There is too much responsibility mitigation here.

So studying and working overseas will do fantastic things for Vietnam. You are already seeing the results of this in junior to middle management. I look forward to seeing more of them move into senior management positions.

Yes, if the opportunity is available. Studying, working and living in another country can only broaden your range of experience by introducing personal challenge and experiencing diversity. There will always be a choice to be made as to whether or not it is the right time to do something. Remain positive and the opportunity will not be wasted.