AUKUS is primarily a technology-sharing group with the single-point agenda of bringing the nascent Australian military capabilities up to par, in order to ensure Australia (or any future government of theirs) doesn't buckle under Chinese pressure, which was actually a distinct possibility especially under Kevin Rudd and even into earlier years of Morrison.
As of trusted allies, Australia was always part of US intel-sharing (Five-Eyes) and mutual defence agreements (ANZUS), nothing new there.
I don't see why people are drawing a line between AUKUS & QUAD - the former like I said is about tech-sharing with single-point agenda of bringing Aus up to par. The latter is about containment of China, a strategic aim that goes above & beyond, and is in the interest of all QUAD countries (and many others in the region, QUAD should actually be expanded).
If by this you mean including India & Japan in AUKUS-type tech-sharing, it won't happen for many reasons. Must say the latter is more likely to be included considering the mutual defence agreements & nuclear umbrella-sharing but Japan may not want/need SSNs the same way AU does.
For example, the diesel sub that AU was planning to get did not even have AIP. But the Japanese domestic industry is way more advanced & their boats include mature fuel-cell AIP along with advanced Li-ion Batteries (LIBs) to extend endurance & power, not to mention the extensive industry surrounding the same - plus their operating distances & proximity to China means their need for a possible SSN is nowhere as critical as Australia's (where range & endurance is of utmost importance):
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But India would definitely not be included (or even want to be included) for various reasons. Some are:
a) Existing independent nuclear deterrence capability, and mature & continuing program for delivery systems
b) Existing independent nuclear-powered submarine programs & required shore-based infrastructure (underground pens, ELF/VLF, refueling/reactor training etc)
c) Even though several intel-sharing & logistics-support agreements exist (like BECA & COMCASA), there's no mutual defense agreement
To put it in short, there's not much for India to gain even IF a similar agreement as AUKUS were put in place - and whatever could potentially be gained would come with way too many strings attached which wouldn't be worth it in the end, especially for a country like India that values strategic & nuclear autonomy.
All the same, strategic (and economic/supply-chain related) containment of China and rebalancing of power is not possible without India & Japan being in the mix. There's a reason why the US' strategic relationship with India (which was bitter as late as Clinton's first term) has been on a constant uptrend over the last 4 US presidents, despite their wildly contrarian ways & methods of approaching foreign policy.
e.g.
Bush Jr - Nuclear deal despite being non-NPT country
Obama - Major Defense Partner ('ally' status in defense deals despite not actually being one on paper) & LEMOA signed
Trump - COMCASA & BECA signed, ignored Kashmir annexation, blocked NASA's bid to sanction India after 2019 ASAT test
Biden - QUAD promoted to heads of state-level, no CAATSA despite S400 deal (so far at least)
Hard to explain all this otherwise.
But what cannot be forgotten is that India is no UK - it's strategic goals will not align with the US 100% of the time. So why is India with US in QUAD? Because right now, with regard to China, the interests do align. And like I said that's what QUAD is about - containment of China.
So while India is no UK, it could be a 'France' - which despite being NATO has nuclear autonomy. Or rather 'France+', as it goes beyond that.
@Nilgiri @Milspec @Cabatli_53