As the last of the Arihant-class are being completed, the next-generation Ballistic Missile Submarine internally codenamed S5 is shaping up to existence. Unlike S4 and S4* which are just an extended version of Arihant class, S5 SSBN will be a new design and will be nearly double the size of the previous S4 (Arihant) class. The S5 will begin construction once the S4 vacates its berth in drydock next year. Being of around the same size as the French Triomphant, BARC will upscale their reactor to 190 MW to fulfill the S5's power needs. It is planned that 6 of these will enter service. All boats are named after Shivan gods, the Destroyers. Each unit will cost $2.2 billion

At the same time, after delays to the Indigenous SSN program, and with the threat of Pakistan purchasing 4 state of the art SSN, the Indian Navy has launched the SNASV program which has chosen to procure 6 submarines in 2 batches, modified variants of the Astute (Minister-class) and Barracuda (Independence)-class, as well as to have seeked a partner to assist the IN in the ISSN program, which have been chosen to be BAE Systems. The ISSN will also be expanded in scope, instead enter service in the mid-2030s, and be a next-generation attack submarine. Each sub will cost $ 1 billion.

(Minister in normal, Independence in bold)

With the nuclear submarine force for the Indian Navy of the 2030s determined, we still need a stand-in for the gap in the 2020s where the only nuclear subs that the navy has are 2 leased Akula II-class. As such, the S4 class will received some minor modifications, producing the interim SSGN the S4xx. As well, the S2, S3, S4 and S4* will be redesignated as SSGNs once the S5 enter service. 2 S4xx SSGNs will be constructed costing $1.2 billion each, as a 120m version of the S4, with 10 tubes instead of 8, and all ships of the Arihant-class (From S2 to S4** will be retrofit with flank and towed sonar arrays) to facilitate ASW.