Cates isn't a top six forward, neither is Frost at this time.
Hopefully they'll develop into those roles.
Frost has to be more consistent, he'll have stretches where he'll score, but scorers go hot and cold, the good ones bring it every night and don't go MIA for long stretches - even when they're not scoring, they're making things happen. Look at TK this season. Frost has a tendency to get passive and wait for opportunities to come to him instead of driving play.
Cates is not a 2C, he may be a 2LW, he's similar to Laughton in that regard, except he's a smarter defensive center, but doesn't have the playmaking skills to drive a top 6 line - though you might team him with someone like Brink. As a LW he'll need to get stronger b/c he'll spend more time along the boards fighting for pucks, but he has great hands in a crowd. But his future is similar to Laughton as a jack of all trades who contributes in various roles, C, LW, PK, PP2.