A recent headline reads, "Periodic table gets four new elements, making science textbooks around the world out of date."
If the teacher needs new textbooks, by all means, he should get new textbooks. Some school systems, though, are strapped. The primary teacher who would need new textbooks would be the chemistry teacher (maybe physical science) who likes to have students memorize the periodic chart.
Otherwise, we're looking for patterns. The new elements--rather, uncommon--will be unlikely to be used.
On the one hand, science is always "out of date." On the other, the basic processes will remain the same. Better is the [old or new] textbook that explains itself well than one with all the latest information. The teacher can fill in any necessary gaps.
On the other other hand, a retired teacher pointed out to me that we assumed that a school was better simply because it had the latest stuff. While getting the latest is irrelevant to a quality education, perceptions can have positive effects: e.g. the white coat effect, the placebo effect.