I agree that it will become full blown citizenship some day. There are several reasons for my belief.
The OCI application process is very different from PIO. It is also handled differently, with approvals coming from Delhi, consulates merely acting as forwarding agencies.
OCI is a very good way to test the legal/political/social/economic/national security waters of dual citizenship. This buffer zone gives plenty of time to iron out any such issues.
All the major political parties support and advocate duality.
India has seen the advantage of having a successful diaspora and like aabbcc11 said, they wanna milk it. Think of political parties which would love to accept political "donations" from its "citizens", for a party ticket or party development funds etc.
India has also seen the benefits of dual citizenship enjoyed by the very influential Israeli Americans, who have shown that a very powerful diaspora in the right places can do wonders in international relations.
Now, how long will that take? That is a very different question!
Nred