I expect it would be technically possible to have lemmy-like or peertube-like services built on top of the AT protocol Bluesky uses, like with ActivityPub. And I expect if/when that happens the communication across services would probably work too.
In fact, accounts being “portable” in the AT protocol can potentially make the integration more seamless across different services, not only might the posts be seen from different services, but you might be able to directly access those different services with the same account. Imagine if you could login in lemmy with a mastodon account or vice-versa.
Bluesky is just one of the possible services. But as long as the invites are private and you can’t host your own instance, I wouldn’t even consider it an alternative. I think it’s a bit early to judge, both its positives and its negatives.