Nobody knows what the situation will be after the current funding agreement ends will be. As part of that agreement, there will be a review of ongoing funding in a few years time. The agreement is at https://www.gov.uk/government/publications/canal-river-trust-grant-agreement-with-defra and the relevant clause states:
" 9.3 Notwithstanding the regular content and cycle of Review Meetings, in the financial year 2021/22 a review will take place to consider whether, and if so, the extent to which there is a case to continue to support by Grant the public benefits (including, but not by way of limitation, provision of land drainage, flood mitigation and other public safety benefits) provided by the waterways under CRT’s stewardship beyond the end of the Grant Period. The 2021/22 Review shall take into account, among other matters, CRT’s performance of its obligations arising under the Grant Agreement. Defra shall issue a report setting out the conclusions of this review with regard to continued support of CRT by Grant beyond the term of this Grant Agreement on or before 1 July 2022. "