The world is, to some extent, already saying it... and as mentioned already, it fits in with the strong delusion. You can see it in the movies, and the "new" theories about how we were created. I also believe this "alien" delusion/deception will fit into the mark of the beast, and the lie of 'you can become like god' being an alleged "dna upgrade" when in fact it will be like the days before the flood, with the corruption of the human genome - a mutant, a beast, an X-man.
Here is what the "new agers" are saying.... the seeds of deception are already planted.
"There is to come a separation of those that accept the gift that the visitors are bringing, and are willing to move into the new world enlightenment and those that do not choose to accept the plan. Those that do not accept the plan are to be moved to another planet until they progress to a point where they will accept it." - - representative of the Aetherius Organization
Well, I know people will jokingly say, "Rapture!" I mean, people will laugh at it for sure while others (eventual Trib Saints) will take it seriously.
However, if the AC is truly the Mahdi for the Muslims, I believe their belief is that he comes with Jesus as his prophet - which would be for us, the False Prophet of Scripture.
If the Mahdi comes on scene with "Jesus", then it would seem another story (other than Rapture) would have to be made up - aliens could explain it, OR, the FP could say in wrath, he judged the fake, intolerant, fundy Christians, leaving the true church behind. Those who don't know the Word from their junk mail will eat it up. In fact, they might finagle some "new scripture" so that no one actually READS the Bible. I think the Word will be outlawed and burned, personally. I truly believe Bibles will become rare and Trib Saints might have to rip pages out of them in order to smuggle them easier. Maybe even trade pages amongst the underground churches.
The Bible speaks of a famine for hearing the Word of the Lord. I do believe that's now, however, moreso during the Trib.
