Remove Keywords From Webpage But Still Use for SEO

You will need to add meta content containing the old keywords, in order to be found. IF you override the old keywords and meta data, it will eventually crawl using just the new words. The key areas are – content, meta-description, title and alt tags. You can leave the old words in, but this means you are using limited meta data space to reference the old ones, which seems like not good practice.

My suggestion would be to add the old keywords to the page tags and leave the rest of the meta data concentrated on the new and active products.