I'm betting half-75% leave then the rest stay.... but that 25% is a hell of a lot better than nothing.
but you also gotta think, when you release bugs that aren't native to an environment you're messing with the ecosystem, maybe not in a signfiicant way, but there are things that jive with your eco system and things that dont... those that don't will die/leave.... those that do will flourish.
it would take a /lot/ of research though to figure out the exact temperments of the bugs you're putting into your environment.
I mean everything has to be in balance... too many wasps eat to many bugs, they run out of food, all die, then the bugs come back... or there simply not the bug for the job.... imo nature always works with synergistic reactions, so when we put /one/ thing out in the environment thinking it will work I think we're asking for failure vs getting several things that coincide well together and the environment...
I realize it probably seems like I"m overcomplicating this, but it truly is a fine balance and if you guys wanna get into using bugs to protect your grow you gotta make sure they jive with your environment and ecosystem.