A very sensible question in my opinion. Generally speaking many consider CA as the ultimate destination and do not look at anything programs further to enhance their career growth opportunities. Some however do take up programs like the CMA (India) or CS to leverage on the commonality of subjects between these programs. Of late there is an increasing awareness for international programs like the CPA, CIA & CMA and there are quite a few looking at these options as well. The advantage of these options are they are short term programs with global recognition and it makes a lot of sense for a CA to complete the same for global opportunities.
The programs mentioned above are part time and can be done when the Chartered Accountants are employed. Pursuing a MBA (either from India or Overseas), which is a full time program, is a different ball game altogether. Let me make one thing very clear before I even continue. If at all a Chartered Accountant decides to pursue his / her MBA it needs to be only from an A rated school and not even a B rated one. It should either be from a good Indian School like the IIMs, XLRI or an ISB or global schools which are top-rated. Anything else is a big compromise and would not recommend that. The rationale behind this reasoning is a qualified CA already has a prestigious qualification and hence he should not be doing his MBA for the sake of doing it but to add or enhance his career opportunities and hence must be only from an A rated school either in India or globally.
Personally speaking would strongly recommend a MBA from an A rated school for a CA. An MBA adequately fills in the shortcomings in a Chartered Accountant and thus makes it a great value add from a career perspective. However there is one important fact that needs to be considered when selecting a school. Majority of the students in such schools come with 3-4 years of work experience and hence it would be an advantage if the CA has one too. Thus if someone is able to complete his CA by 22 or 23, would strongly recommend him to acquire about 3-4 years of good work experience (during this period he can try and complete his CPA, CIA & CMA from the USA) and look at a MBA from a school of repute. This would be the proverbial icing on the cake and help the person carve a niche for himself in his career. In case the person is able to complete his CA a little later, say around 25, it would depend on him as to when he would want to get married and settle down. He / She can take an appropriate call since there are other factors that are involved in this decision.
To sum it up, an MBA from a school of repute would be an awesome value add to a CA.