There's no guarantee. If we see another event of retro shard avis coming back like we saw this past ATA day then it's possible, but I don't think anything can be said for certian at this point.
At this time, no. You cannot get the avis. But like Witchee said, ATA may do something unexpected again and have different throwback shards at some point. We have no way to know. You can ask general game questions on this thread, or in the #advice channel on the pimd discord.