That's the biggest concern: being able to use the interface the way you have for ages without having to RE-familiarize yourself. This seems to be a harder hurdle for non-technical older folks. The gmail app interface changing every so often on android tablet would cause parents so much confusion that I finally replaced the tablet with a linux laptop with thunderbird
Biggest word of warning though is that Google are totally happy to change things with no warning or how or why, which can be very confusing.
For example, they stopped a direct route to import photos from an SD card or alike to google photos. No automated replacement workflow.