Right, but it's partially speculation based on knowing what has nearly killed the band before.
Rattle & Hum faced a poor reception, they questioned their existence, gave re-invention a shot, the recording process nearly tore the band apart, but they rebounded spectacularly with Achtung Baby.
Pop faced a poor reception, they probably questioned their existence, gave a re-invention of sorts a shot, by all reports the recording process was very smooth, they rebounded spectacularly with ATYCLB.
No Line faced a poor reception, they no doubt questioned their existence to some degree (does the world really need or want another U2 album?), the recording process has taken forever and there's a chance that this is in part because it's been 'difficult', whether or not they rebound this time remains to be seen. Throw in age and the fact that distractions away from the band now have at least equal priority, and it's really not hard to see that a scenario of, well, what if there's no spectacular rebound this time? What if the answer to 'does the world need or want another U2 album' appears to be 'nope, not really'? It's not crazy talk, they've kinda laid the scenario out themselves.