It could work, but in a certain way. I think what they ment is having a console be faster not necessarily a PS5 spec like console.
The way they could approach this is, enabling full SSD support, that alone would make loading times faster. On that same PS4 they could add PS1, PS2 chip for backwards compatibility. Maybe add 1gb or 2 of more ram for faster multitasking purposes.
All of what i suggested would simply make this a PS4 for the enthusiasts but of COURSE you would have to pay more. Games would still be the same etc. I know I would buy one of these if it came true.
Mathrym's comments