Seriously, I doubt it would even take that long. We get used to shit so quickly, and the news cycles have to keep feeding us new things, the only way we’d keep talking about the aliens if they kept doing new and interesting things. I’d be willing to bet a year later there would be some people who straight up forgot about it. “Oh yeah, aliens! Are they gonna, like, visit at some point or just keep exchanging calls with the Whitehouse?”
Unidentified Flying Objects have always existed. In the US, around 99% of submitted cases were identified eventually or revealed to be bogus. The remaining 1% exist, but the track record of identified stuff doesn’t give the alien explanation a high likelihood.