If Bitcoin Cash really is a pump and dump, then we may see it drop out of the top 5 if there's a large dump.
Other than that, I personally believe that NEO is the strongest contender for the #6 spot, possibly higher. I fully expect that NEO will break the $500 mark by Q4 2018.
Someone is really pumping a lot of money in it. Not saying that's not the objective but it's an awfully big risk to pour this amount of cash into a coin you plan to dump. Especially considering there may be lots of people who come out of the woodwork down the road if the price were to truly moon. People who had BTC and thought BCH was junk, only to realize they have BCH from old keys.