We should not keep all our forex in USD.
As much as it is tempting, a currency without backing is naturally bound to go in a state of shock in some time if not now. Therefore keeping liquidity in other critical currencies like Euros and Renmibi would make sense. Rouble is anyway not really sustaining itself and since China is our largest trading partner, we could move towards considering a Rupee-Renmibi trade agreement.
Imagine, $100 billion worth of trade done in Rupee-Renmibi.
Also, India is on the verge of signing currency swapping agreements with rest of the BRICS countries. At 30% expected annual growth rate of the trade among the BRICS, this can really give us that cushion to absorb shocks of currency fluctuations vis a vis the US dollar.