Good question, because surely there must be other privacy focused wallets and services under their radar, i saw a few people mentioning Wasabi in bitcointalk, i don't know if it is just speculation or if there is actually any hint at that.
It's possible Wasabi could be next, but I think they played a bit smarter game than Samourai developers.
Coinjoin is not illegal, but they can always make some bitcoin address connections with ''hackers'' and blame them for them.
Government is so very lucky to always have ''evil'' hackers from N.Korea and other countries for that purpose

Yeah, most likely Wasabi and Sparrow are now in the cross-hair of the US government agency and maybe just gathering enough data to nail down the owners just like what they did to Samourai.
There is no real reason to touch Sparrow wallet.
They didn't directly do anything except providing different interface to Samourai wallet, and in latest version they removed all that from their code.
The next to fall? It could be another wallet, a mixer, or anything that makes them think it's used to launder money, which is really stupid. That is why it is normal that every day there are more services available only on .onion domains. It's not always about hiding something, but about being able to use it freely.
Or maybe a cryptocurrency forum?

They like to mix things, so maybe they will take a break and move on some exchange next.
Now would be the best time to improve security and privacy for any crypto service.