SQLScript is not always procedural. Of course we do support imperative logic which is executed in a procedural manner, but we do also support declarative constructs such as CE functions in SQLScript. Intermediate implicitly defined table variables can be used with SELECT statements as well as the set of CE functions within SQLscript today, which I think would satisfy the requirement for CTEs.
As for support for CTEs, I don't see anything in the backlog at this time.
Cheers,
Rich Heilman
HANA Product Management