You don't need the GPL for that; just provide the source code for your software. If users actually care about having the code, they can use your binary for which code exists.
If they don't care, they can use proprietary software, or proprietary extensions that make your software better.
Either way, the user has full control over their choice of software, and nobody's actions can make your original open source code disappear.
The GPL is really about enforcing your ideals onto other people's code if it happens to be reliant on yours. That's a legit quid pro quo for a license, but it has jackall to do with freedom or user rights.
If they don't care, they can use proprietary software, or proprietary extensions that make your software better.
Either way, the user has full control over their choice of software, and nobody's actions can make your original open source code disappear.
The GPL is really about enforcing your ideals onto other people's code if it happens to be reliant on yours. That's a legit quid pro quo for a license, but it has jackall to do with freedom or user rights.