Two fatal errors here:
This document lacks required Security Considerations and IANA Considerations sections.  It can’t proceed without them, and I can’t review the document properly from a security standpoint without the former.

Other comments:

In the Abstract and Introduction, a nit:
“is already well established” should not be hyphenated, as it’s not a modifier (whereas “a well-established pagination pattern” is correctly hyphenated).

— Section 2 —

   The following table describes the URL pagination parameters requests
   for using cursor-based pagination:

I think the word “requests” is extra and should be removed (or perhaps “using” should be replaced by “requesting”).

In the second table you say “Use of previousCursor is OPTIONAL.”  That seems to say that using it in a subsequent request is optional, which is already said in the previous sentence.  I think this one should say, “Returning previousCursor is OPTIONAL.”

— Section 2.3 —
This seems to make this not backward compatible: a client that doesn’t support this won’t know what to do with the nextCursor parameter and will likely not work correctly.  Is it not worth making that clear in the text?