It contains many new features, such as property hooks, asymmetric visibility, an updated DOM API, performance improvements, bug fixes, and general cleanup.
I wouldn’t call it “major”, I don’t see anything too interesting there, but that’s just my modest opinion.
Regarding SuiteCRM, I guess the attitude is to always try to keep up with PHP updates, although try is the key word here 
I guess the really hard upgrades were from 7.x to 8.x, and they’re mostly done.
I expect the transition to 8.4 to be relatively easy, but still it might not be too soon, there’s so much to be done, and these boring parts of the maintenance of a large code-base are much more laborious than most people realize…
That’s true! The SuiteCRM 8.8 will use PHP 8.3 as per this roadmap 
Beta version of SuiteCRM 8.8 using PHP 8.3