It can be "these staff meetings" too. Збо́ри is a pluralia tantum noun (like the English glasses, trousers, scissors, etc.), its plural form can be used either for one event of for several events.
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It's not wrong but sounds worse. Comprehensive rules (or rather recommendations) for that are quite tricky, though. In general, between consonants ‘у’ is preferred: будуть у середу. In the beginning of a phrase or after a pause (marked by comma, dash etc) it's exactly how you say: ‘у’ before a consonant and ‘в’ before a vowel.