As you may already know, enchantments are some of the most challenging types of permanents to remove, so being able to attack and then hide as a noncreature is an excellent way to bypass sorcery-speed removal
While this can be a threat, and you should watch out for growing Ornithopters, most of the time that means that you will take no combat damage and more than half of all decks rely on combat damage to win the game
It's going through the roof no matter what is written on the card. With the usual caveat that this is not investment advice (doing your own research is priceless!), if you want to brew or play with Vivi you may want to keep and eye on Quicksilver Elemental
Ultimately, while this scenario does feel likely, theres no guaranteed when, or even if, itll actually happen
Other variants are a bit more difficult to deal with
It is big, powerful, and in your face