While the latter is more likely given that our governments have done exactly this in the past, there are some reasons to believe that if aliens were to warm up to the idea of contacting us, it might be pretty soon.

We have global communication networks now and are rapidly approaching AGI. For all we know we could be on the verge of a critical inflection point for our civilization that might make it worthwhile to interfere.

Also, the idea that we've been under quarantine up until now is a pretty compelling explanation for the Fermi paradox.