Here is an updated list of old gen non-legendary Pokemon families that are yet to appear in the Kalos Dex
Kanto
Rattata, Spearow, Clefairy, Vulpix, Parasect, Venomoth, Persian, Primeape, Growlithe, Ponyta, Seel, Grimer, Drowzee, Krabby, Voltorb, Lickitung, Koffing, Chansey, Tangela, Scyther, Electabuzz, Magmar, Porygon, Omanyte, Kabuto, Dratini
Johto
Chikorita, Cyndaquil, Totodile, Spinarak, Togepi, Natu, Sudowoodo, Aipom, Sunkern, Unown, Misdreavus, Girafarig, Pineco, Shuckle, Corsola, Skarmory, Phanpy, Stantler, Tyrogue
Hoenn
Treecko, Torchic, Mudkip, Wurmple, Seedot, Taillow, Shroomish, Slakoth, Aron, Numel, Spinda, Cacnea, Baltoy, Lileep, Anorith, Feebas, Castform, Duskull, Tropius, Snorunt, Spheal, Clamperl, Beldum
Sinnoh
Turtwig, Chimchar, Piplup, Starly, Kricketot, Shinx, Cranidos, Shieldon, Cherubi, Shellos, Buneary, Glameow, Stunky, Bronzor, Spiritomb, Finneon, Rotom
Unova
Snivy, Tepig, Oshawott, Lillipup, Munna, Pidove, Blitzle, Drilbur, Audino, Tympole, Sewaddle, Cottonee, Petilil, Darumaka, Maractus, Yamask, Tirtouga, Archen, Minccino, Deerling, Frillish, Alomomola, Joltik, Klink, Tynamo, Elgyem, Bouffalant, Rufflet, Vullaby, Larvesta
There is still 36 spaces left (1 in Central, 12 in Coastal, 23 in Mountain).