Ranking the centers in the league right now is a really difficult and subjective task, but I came up with the following:
1A: Getzlaf, Eichel, Bergeron, Toews, Seguin, McDavid, Draisaitl, Barkov, Kopitar, Tavares, Crosby, Malkin, Stamkos, Matthews, Backstrom, Scheifele
1B: Kesler, Krejci, Monahan, O'Reilly, MacKinnon, Wennberg, Spezza, Zetterberg, Carter, E. Staal, Johansen, Turris, Giroux, Thornton, Couture, H. Sedin, Kuznetsov
2A: Duchene, Anisimov, Koivu, Stepan, Zibanejad, Stastny, Kadri, Nylander, Johnson, Horvat, Little
2B: Backes, J. Staal, Rask, Backlund, Dubinsky, Nielsen, Larkin, Nugent-Hopkins, Zajac, Brassard, Couturier
In my opinion it's virtually impossible to categorize certain players if the only distinction you use is '1C or 2C', the difference between the worst 1C and the best 2C is so minimal it might as well be non-existent.
With that said I think both Patrick & Hischier will almost certainly end up in the 1B / 2A group, obviously there's still some variation within those groups, but I think that's a fair estimate for the caliber of player they will become. There's a slim chance Patrick becomes a Kopitar/Getzlaf level player, but I think it's more reasonable to assume he'll be closer to guys like Johansen & E. Staal.