I am somewhat more in favor of "speni .uaigre" than of ".uaigre speni",
but the former had morphological issues/concerns. I think that this
construction can be justified by taking the view that Lojban treats all
times somewhat equally or elliptically; "speni" does not mean simply
"(current) spouse" but also "future spouse". Thus, this construction
specifies that the 'tense', so to speak, is future and not current (with
no implication about the past), meaning that the type of spousal
relationship here is a future-and-not-current spousal one.