The chances of us getting Diego Garcia anytime this half-century, or even in the whole century, are virtually nil. One thing you should learn from America's history is that it NEVER compromised on its interests. Not even in the 1700s, when it was of virtually no importance in the world. America rose to such prominence because it aggressively pursued its interests without regards to anyone else. Now compare that to India's "soft diplomacy" approach which aims at pacifying everyone and their dog. I'm not saying India's diplomatic approach is wrong, but we simply aren't going to manke any "hard" gains through such an approach. Maybe our approach will change as the balance of power shifts in our favour, and then we can discuss displacing America as the dominant power in the Indian Ocean (which, btw, I think should be a long-term strategic priority for India).
As for foreign bases, our priorities should be:
1) Tajikistan - to obtain access to Central Asian oil, counter Chinese influence in the region, and secure our northern flank. The main hurdles here include collision between Russian and Indian interests and the lack of a direct land route between India and Central Asia. The first problem can be solved through further diplomacy, the second by the eventual reunification of Kashmir.
2) Mauritius/Madagascar - as a base from which to exert influence in the southern Indian Ocean. This is exceptionally important due to our lack of access to Diego Garcia.
3) Mozambique - as a base to protect India's rapidly growing interests in East Africa.
4) Vietnam/Indonesia - to secure the strategic waterways of Malacca, and cooperate directly with ASEAN.
