Google's 7-Year Update Promise, what do you really think?

Google's commitment to 7 years of updates is a big deal, but I wonder if it’s sustainable. Will we actually be getting meaningful updates for that long, or just security patches after year 4?

Apple has done 5+ years consistently, but Android brands haven’t had the best track record. Will the device even stay smooth for that long, or will it be another case of "updates slowing down older devices"?