The article you've posted points out that the IN has already decided on the vessel's components & specifications. The 2030 date seems to be based off the worst-case scenario, i.e. in which India would have to develop a shipborne nuclear reactor from scratch and that the project would be susceptible to delays stemming from the Vikrant program. As the Diplomat has pointed out, the Vishal could potentially use one of three options for its propulsion: (1) develop a reactor with the United States (most likely Westinghouse), (2) scale up the reactors used by the Arihant, and (3) navalize one of its commercial reactors.
Additionally, we do not know which shipyard the Vishal would be built at (either Cochin or Mazagon), so it might not actually be affected by the Vikrant program.
Umm, no. The Indian Navy has decided they want EMALS on the carrier, they've decided they want it to displace 65,000 tons full and have about 55 aircraft.
But apart from that they have yet to finalize a design, and you yourself have even said that they have yet to even settle on a nuclear propulsion system (which is probably the most vital part of a CVN to begin with).
Put all that together, along with the atrocious programme management causing delays, which seems to compound all recent, indigenous big ticket projects of the Indian Navy (P15A, INS Vikrant, P17) between launch to commissioning, and I think an early 2030s in service date is actually pretty reasonable if not optimistic.
At the very least you can surely admit that a 2025 service date is impossible, as such a service date means it would need 1-2 years of sea trials prior to 2025, not to mention at least 1-2 years of fitting out prior to sea trials, and a ship of that size and complexity would need at least 3-4 years of construction prior to launch.
That means if INS Vishal really wants to be in service by 2025 it would have to begin construction of the first modules either this year or next at the very latest -- and that is assuming the Indian shipbuilding industry is able to do the job in the timely fashion listed above which is what you'd expect for a US shipyard, UK shipyard or a Chinese shipyard, but which given the track record of Indian shipyards I wouldn't be surprised if construction from module fabrication to launch takes double that time and fitting out even longer.
Or let's put it this way -- from where we stand now, the INS Vishal as about as good a chance of entering service in 2025 as the INS Vikrant does of entering service in 2018.
If it turns out that the Indian shipbuilding industry somehow gets its act together just as they start constructing INS Vishal, or if they receive massive, useful assistance from the US industry, then sure, that may change things, but those are the equivalent of unforeseen acts of god from where we are right now.
Back on topic: the Chinese should find ways to maintain their current lead in light of naval expansion programs by both the Indian and Royal navies.
China's naval priorities are dependent on what its strategic interests, are, not to seek whatever degree of "lead" over other navies for the sake of it.
I'm also not sure what you're particularly concerned about -- consider the Chinese Navy in 2025 and think about how many 055s, 052Ds, 054Bs and 054As they have in service by then, and look at the construction and commissioning plans for other navies around the world and their destroyers, frigates and carriers, then re-examine the issue a little.
