I think they are being used already by blockchain analysis firms and very likely a wide variety three letter agencies. This is why I expect more whales to eventually use Blockstream's Liquid because of its fast and private transactions. The only thing Liquid is lacking is more exchange based adoption, but that's just a matter of time.
I must say though, whoever moved that many coins, it's massive free advertising for the whale alert Twitter operator. This news has been covered here on local news channels more than once today.
Yeah, massive advertising. Wonder who owns it, got to be chanalysis/3-letter agencies.
And probably a good point on using Liquid -- they already got a few of the big guys on it, in fact on Xapo and BitMEX alone they already have enough Bitcoin between themselves to facilitate a lot of confidential whale transactions. The question is, do the whales still doing stuff on-chain want to identify themselves to Blockstream et al? A whale may conceal their txs on BTC public blockchain via Liquid but it's still a huge ask to have any number of Blockstream people actually knowing who they are (to me, anyway).
Could another possibility be that these whales would also form a federation of LNs and keep it all completely off-chain?