Disposition of property ahead of a testator's death

When you have already executed a will in favour of your sons (ciizenship has no relevance in devolution of the property) there is no need for any other document.

If you want to  sell the property it is entirely upon wish / magnanimity of the vendee (purchaser) to allow you to use it during your life time, which is generally, not acceptable.

You can transfer the sale proceeds to your sons' NRO accounts, but this will be legally treated as a gift during your lifetime rather than an inheritance under your will. Because you are selling the property now, your will which only takes effect after death does not yet govern these funds. 

Since you are a resident Indian and your sons are non-residents, transferring money to them is governed by the Liberalised Remittance Scheme (LRS). 

You can gift up to USD 250,000 per financial year to each son. If the 50/50 share for each son exceeds this amount, you may need to stagger the transfers over multiple financial years or seek RBI approval.

Transfers exceeding ₹7 lakh in a financial year will attract a 20% TDS. You can claim this back as a credit against your own income tax liability when you file your returns

Thanks, folks, much obliged!

Have you taken your sons into confidence as to the proposed arrangments?

Once the property is sold, without or without conditions,a fresh Will needs to be executed based on the changed circumstances.