Cydia has been a massive part in Jailbreaking for many years and is the main part that handles purchases on Cydia. However after a recent bug was disclosed to Saurik, the creator of Cydia, he closed the payments section to protect users and then on Friday evening he made a statement on Reddit:
The reality is that I wanted to just shut down the Cydia Store entirely before the end of the year, and was considering moving the timetable up after receiving the report (to this weekend); this service loses me money and is not something I have any passion to maintain.
Cydia itself will still be around, however, the backend for payments (on the main repositories) will no longer be in service. You will still be able to download past purchases and make purchases on third-party repositories. Saurik says that a formal post is coming next week with further details regarding the future of the Cydia Store. His full statement can be found here.