Firefox 7 isn't even a real release. You'll have to wait for 8. The new versioning system uses the Fibonacci sequence, so that after 8, the next "real" release

Firefox 7 isn't even a real release. You'll have to wait for 8. The new versioning system uses the Fibonacci sequence, so that after 8, the next "real" release will be 13, and then 21 etc. This is why you're currently stuck on 5.