It could be, but the question isn't so much of stellar's promise but as to what coin will be replaced in the top 5. Bitcoin, Ethereum and Ripple seem fairly nailed on, EOS seems to be going strong and if they deliver will likely challenge Ethereum for no 2 spot. The most obvious candidate is bitcoin cash but it still seems to have a lot of support in the market.
Being in the top-10, Stellar can easily get into the top-5 coins. I guess, we will celebrate this event already in 2018. I am holding Stellar alts as it is a very good coin:
https://www.youtube.com/watch?v=3zTpnOMwO9s