Apple does not pre-announce end-of-life for its products.
Most models of iPad maintain full update support for five to seven years. The iPad5 was released March 2017 - this approaching six years. While it is impossible to provide a definitive statement as to availability of (and compatibility with) future major versions of iPadOS, you might reasonably infer that while the iPad5 is still supported, its time may be running out.
Your iPad5 supports iPadOS 16.1.1, but not support some of the newest advanced features. Given your stated use, if considering a replacement iPad, both the entry level iPad9 and newer iPad10 are both entirely suitable for your needs and support the majority of the current iPadOS16 feature set. Both the iPad9 and iPad10 are expected to benefit from future major-version updates.