Bangladesh, Vietnam and Egypt are good contestant if BRICS want to limit its member country to 9 and if mexico and turkey is kept out due to US influence.
Case for Bangladesh as it is likely to grow with 7.5% gdp growth rate in between 2010-2050 which is the 4th highest in the world. But it has potential to grow at more higher rate. High population. Potential manufacturing base. Even distribution of wealth, geographical proximity and as a neutral member good relation to all country in the world. Lastly for its big population.
Vietnam is also expected to grow at a rate of 7.5% in between 2010-2050. Present development is impressive. Future prospect is bright.
Egypt highest population among middle eastern countries. Potential to be in the top 10 economy by 2050. But growth rate is expected around 6.5% only between 2010-2050.
The projected growth rate is based on page 11 of Wealth Report 2012 by Knight Frank & Citi Private Bank.
http://www.thewealthreport.net/The-Wealth-Report-2012.pdf
South Africa is the odd man out in BRICS.