SAP had the opportunity to redevelop R/3 into a more 21st century kind of software. Instead, it wasted money and resources in HANA, which seems like a useless piece of c-ap after all the hype.
Imagine the shock I had the first time I opened ME21N (it was through a menu system instead of t-code) in a Fiori-based S/4HANA expecting something revolutionary - the shock that nothing much has changed since R/3!
Those who tell you S/4HANA is The Future has never logged in to a R/3 or S/4HANA system before.
To address the above post by @Ybu9JGj-1sht, no, customers don't find the need to upgrade because S/4HANA is like R/3 in a different coloured-shirt and shades! Business users also dread to go through the entire re-implementation again, only to use back a similar system with a different "coloured-shirt"! Customers are no longer that gullible and the only thing SAP can do to push S/4HANA licenses is through license audits.
Better jump before the Titanic sinks! At least you may survive!