Artwork of Canada's British Columbia based (current or future) Cellula Robotics Solus-XR XLUUV - see brochure.
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Further to my article "Canada's RCN Using the RAN's Attack-class Plan?"
of April 14, 2023:
If Canada orders new SSKs after several reviews it may receive them in about 15-25 years. As Canada's Upholder/Victoria-class SSKs were launched in the UK between the mid-1980s to early 1990s then the "youngest", Corner Brook and Windsor, might last until 2030, if there are no major life-extension overhauls.
Canada (like Australia) might well be hedging against a substantial No-submarine capability gap (say) from 2030 to, say, 2045, by investing in XLUUV development.
We live in a world of ever more capable unmanned submarines, that are vastly cheaper than manned subs. As XLUUVs are large (say 1.5m diameter and more than 10m long) they may finally attain an unrefueled range of 5,000nm. This is enough to cross the Atlantic (Canada to Spain - see Cellula's map scrolling half way down) or Australia to Hawaii (or Aus to Diego Garcia). They might not be able to launch from any Western submarine, other than USS Jimmy Carter, so rely on pier side launch.
Future Canadian XLUUVs might gather intelligence (say) with onboard passive sonar for ASW, mine countermeasures and concerning drug smuggling in the Caribbean and off the Pacific coast of Central America. Against China and Russia laying seabed or tethered sensors and even smart-mines may be a quiet future function.
The RCN may be looking at several XLUUV solutions. I'm aware of Canada's British Columbia based Cellula Robotics Solus-XRXLUUV - see brochure (artwork above). Canada's economy being capable of developing formidable XLUUVs is another incentive to build them.
The RCN (like the RAN?) may also have a watching brief on the US Orca Program. Although Orca's huge size, consequent high cost and USN domination of the Orca Program might be a turnoff. Alternatively Canada (and Australia) might be members of a quiet Orca Operational Coalition with Canada and Australia serving as pier side refueling stops for transitting or return leg USN owned Orcas.