My thoughts on this:
*The Wraith don't tolerate rivals that could challenge them so if they had such an ability, they would have done so long ago to defeat the Asurans. Not a definate but something to consider because remember that they destroyed any Human civilization that would rise technologically because they don't want to be threatened by something that could end up like the Lanteans which the Asurans represent in some way.
*The Asurans have no need to expand beyond Asuras. They don't appear to want some form of empire to govern or slaves to rule plus they seem very isolationist so they could perfectly be happy on their little world without any need to leave. I mean they have perfect power requirements, 'food' requirements and everything so there is no reason to leave beyond expansion.
*Every single part of the Asurans are programmed to attack the Wraith so, while not stated, their plan may consist of active deployment of their very own nanites on the Wraith to kill them. We have seen the nanites actively and aggressively target and exterminate Wraith tissue already so it wouldnt be that bad a plan depending on whether they can actually deploy the nano virus on Wraith ships and worlds. Alternatively, they could just kill all Humans and starve the Wraith.
*Its not that inconceivable that the Asurans remained undetected for so long. As we know, Wraith hyperdrives are kind of poor in terms of speed and depending on where Asuras is located, the planet could very well have been too far for a Wraith ship to actively stumble upon it but thats just conjecture at this point.



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