Painther,
The figure of 350 000, was not a prediction, I referred to it as an estimated current Qatari native population.
The math is easy to calculate.
Just at this moment (forget about future mega projects), if you take the Qatari native population (30%) into account and exclude the temporary one (70%), Qatar has already overbuilt for the next 5 to 10 years. The Qatari population can no longer be in charge of their country on its own.
They only have two choices:
- To maintain control, develop in accordance with the population growth;
- If they choose to overdevelop (which somebody did) then expect to either share the country with a majority of foreigners and in this case to justify for the long term the overdevelopment, to start an immigration policy just like other new nations (Canada, Australia, etc...).

If they overdevelop counting only on Qataris as full rights citizens and a floating transitional population of migrant workers and expats, this society will never mature as this last group comes here to collect salary and leave. The minute oil and gas runs out, they will stop coming here and the over development will be just too much to be handled by Qatari only.
Can you see what will happen in this scenario?