This was actually brought up on the Community Council. Here is the post:
You can give a like to the post even if you’re not part of the council. I’m wanting to share this post around so it can get as much support as possible.
I’ve been wanting to get more slots for my account for awhile now. I’m dangerously close to the cap and don’t want to delete characters if new races and classes come out. I also don’t want to have to manage more than one account with their own subscription and such. As I’ve said before and speaking for myself, I’d happily pay to get more character slots for my account.
I hope more character slots per account is something considered someday!