Re: 5 years
"In short: end of all development for the platform."
The life support for Chrome devices is for the hardware, not the OS. The OS hits a new version every 6 weeks and is a gradual development, so you won't get a Chrome XP followed by a Chrome 7/10 several years later and be stuck without updates.
You *will* have no updates after 5 years, but there is no indication that development of the OS will end, and newer devices on the same OS version number will continue to be updated.
And you definitely won't get a Chrome Vista!