No and Yes.
If you are renewing a support contract (Software Maintenance Service), then Mathworks historically permitted you to back-pay up to (I think it was) 3 years to bring your contract up to date without having to purchase the software again. If you have been up to date on support contract payments, then everything is transparent, you just pay the current rate.
However, if your software support is more than 4 years out of date (my memory is fuzzy about between 3 and 4 years), then Mathworks historically required that new licenses be purchased against the current software version.
This is, however, not a requirement that you use the new version: except for some student licenses, a license entitles you to use all versions prior to that as well. Also, technical support is generally only offered on a given release for two years, after which Mathworks would tend to suggest upgrading (in most cases it isn't practical for Mathworks to keep supporting older releases.)
You would need to check with Mathworks Sales for the current boundaries on the number of years of back-payment permitted without re-purchase.
