We don't know that Contact with (the right) nonhumans will result in interstellar travel (presumably via wormholes) - at least where there isn't too much of a time lapse between departure and arrival back home. (Is there a universal real time where traveling to other solar systems and back would be the same as flying overseas for a week's vacation)? We don't know if we can achieve ecological balance with clean and free energy, and other Earth-friendly products and methods, in our formally aligning with "ET." We don't know if there will be a revolution in health care/medicine in general where the costs won't be insanely expensive as today (if not completely free). There are probably many other scientific and spiritual advancements, imaginable and unimaginable, that may or may not be realized. However, we will never know until we've tried to improve our collectively too-largely sorry, pathological lot in life.
There simply isn't enough that's truly substantial enough to show for the stranglehold that religions and corrupt-by-definition secrecy-based government(s), the 2 primary obstacles to progress, have had on humanity, so what do we really have to lose by forsaking the paradigm we've known? Face it: The rate of human population explosion in tandem with industry as we know it isn't a sustainable model. Pollution and depletion of resources magnify exponentially every decade or so. Under the present system the human race can survive merely decades rather than centuries, or virtually certainly not a full 2 centuries, and that's not even getting into the scientifically-proven climate change/global warming reality. No one has the right to bestow a living Hell, environmental and/or sociological, upon our descendants.
Wouldn't it be indescribably wonderful and beautiful if, for the first time ever, humans could attain real meaning and intelligence in our existence - either at least before we burn ourselves out or to in fact save ourselves and the planet?
True that, no matter how you slice it, such a new way of life will or would be a huge shock initially. There's no reason to believe, however, that the shock will be an unrecoverable or too devastating one. I believe the key to adequate shock absorption is in letting everyone know from the outset that, one, effectively everything into which we've been indoctrinated (politically and religiously) is wrong, or at least inadequate, and two, that being brainwashed into beliefs instead of taught with (enough) objective facts is normal. The minority of us that's been able to see through the Orwellian government and media propaganda (lies, or enough so) is abnormal. Doesn't mean we're wrong or bad, of course, just not of the norm (in this era/paradigm). Simply always show as much love and respect as possible.
Being on the right side of history means for all of the future - eternity. What are the chances those who choose to be ignorant of the most important issues today will have any moral authority in the long run? (crickets chirp)