Learn English – Which tense should a verb take when parentheses could alter the tense

In the following sentence I'd like to convey that "I don't know what space an item currently takes up or what space it will take up at some undefined future time". I contracted the sentence using parentheses* to read:

I don't know what space it (will) take up.

My memory of primary school tells me that a sentence should still make sense if the bracketed section was removed, meaning I would have to conjugate "take" as if it were present tense. When I read this, however, it sounds wrong.

I don't know what space it (will) takes up.

Should I always favour the way the complete sentence reads, in this case, conjugating for the future tense?

_{*brackets [BrE] but my programmer mind is often tuned to AmE alternatives.}