For those considering retirement to another country, the best immigration option is dual citizenship. The catch, of course, is that not many countries allow this.
Countries that allow dual citizenship, such as Australia and the US, allow their citizens to become citizens of other nations. For example, an Australian citizen can become a citizen of the US, while still keeping his or her Australian citizenship.
A common misconception among those who read news in the Indian media is that India now allows dual citizenship. Unfortunately, this is not true. What India does allow (only for people who are Indian by descent) is a status called Overseas Citizen of India (OCI). Note that the word "dual" is missing.
India does not allow dual citizenship, and there doesn't seem to be any plan to allow this in the future either. If you hold an Indian passport and become the citizen of any other country, your Indian passport immediately becomes invalid. Yes, you can then apply for OCI status, but it is not at all the same as being an Indian citizen. It is roughly analogous to a permanent residency status.
Overseas citizens get the following benefits:
1. A lifelong multiple-entry visa for traveling to India.
2. Permission to stay indefinitely in India without having to "report" to any authorities.
For those considering retirement or a long stay in India, OCI is a good status to be in, and I am glad that this option is available.
By the way, one could argue that even the US does not allow dual citizenship. This is because when you become a naturalized American citizen, you are required to take an oath where you renounce your allegiance to all other nations.
Here is the exact text of the relevant portion of the oath:
I hereby declare, on oath, that I absolutely and entirely renounce and abjure all allegiance and fidelity to any foreign prince, potentate, state, or sovereignty of whom or which I have heretofore been a subject or citizen.
So even if India did allow you to keep your Indian passport, it would be difficult to claim with a clear conscience that you are a "dual" citizen when you have formally renounced all allegiance to India.