The PlayStation 4 Neo is slightly different internally from the current PS4. It's not a gigantic jump in power, but it is a notable lift. Here's the full rundown, care of leaked specs:
—It's got the same main processor, but it has been tweaked to run slightly faster.
—It's got a new graphics processor that's far more capable than the current PS4's graphics processor (just over twice as powerful).
—It's got the same amount of memory, but it's also been tweaked to handle more equations.
All of which is to say: No, you don't need to replace your current PlayStation 4 with Neo.