Does Michael's employ other kinds of artists or crafters full time? Painters, beaders, knitters, scrapbookers, etc, that do what you do: create finished pieces using the materials the chain sells, for use as store decoration or for sale, as is or as custom orders?

If they do, you probably don't need to worry about your job being phased out. If they don't... yeah, should wonder when they'll decide they don't need floral designers either.

But, you don't need to worry too much. With your skill I'm sure you could find better employment, should you need it. (And learning to handle live flowers won't hurt).

Good luck.