it is possible, but Vrykul could also be another race, like night elves are to blood/high elves they would fit the new race category, whiles human forsaken can only fit the sub-race or racial faction categories.
however Vrykul could be squeezed in as racial faction (sub race/minor race) in the horde or in the alliance under human. I did a list of racial sub-groups in other topics, it's a favourite subject of mine as I would love to play the other factions of the races. In game currently we can only play one faction of each race. You can play a bronzebeard as dwarf but not a dark iron or wildhammer, an orc but not a mag'har orc or dragonmaw. If i were to give each race 3 racial factions here is the list i'd probably go for.
Forsaken Racial Group:
1. Undead Forsaken
2. living human forsaken
3. Darkfallen (undead forsaken elf)
Human Racial Group:
1. Stormwind human
2. Vrykul
3. Half-elf human
Orc Racial Group:
1. Durotar clans orc (normal green orc)
2. Mag'har Orc
3. Dragonmaw Orc
Dwarf Racial Group:
1. Bronzebeard (ironforge dwarf)
2. Wildhammer dwarf
3. Dark iron dwarf.
Troll Racial Group
1. Darkspear jungle troll
2. Amani Forest troll
3. Drakkari Ice troll or Original Zandalari Troll
Gnome Racial Group
1. Normal Gnome
2. Mechagnome (new gnome model but machine look)
3. Leper gnome
Tauren Racial Group
1. Mulgore Clans Tauren
2. Taunka
3. Grim-totem Tauren (these will be dark fur toned tauren)
Night Elf Racial Group
1. Night Elf
2. Highbourne
3. High Elf (could also be human racial faction)
Blood Elf Racial Group
1. Blood Elf
2. San'layan Elf
3. Fel Elf or go for Wretched/Wanted
(not sure how we would do wretched model, could use the new undead model, but with blood elf skins and features adapted with the wretched defects)
Draenei Racial Group.
1. Draenei
2. Broken
3. Eredar (this will need a development - group of dranei sent to infiltrate legion? group of Eredar defectors from the Legion? Velen finds a way to purge the mind/spiritual corruption of Eredar, in a similar way a forsaken cure came and it only works on some Eredar who were forced into man'ari)
Common things to note about the Racial sub-factions
1.They all (nearly all exist in the lore currently, those that don't like human forsaken and eredar are quite conceivable)
2. Some of the options offer a different ideology to the main ones were use to playing, a player may never have an interest in playing a durotar orc b/c he feels these guys are brutes that pillaged azeroth and stupid enough to drink demon blood and doesn't buy they're redeemed, but may be willing to play a mag'har orc that's kinda pure.
3. Notice the racial factions can all have some slight cosmetic variations to the main racial faction we already play. Since we're getting new models, blizzard would be smart to introduce the models with options that now include the remaining racial factions of the race we never could play. Note how each racial faction can use the new race model but with slight variations like skin tones, eye colour. extra features, there will also be some cross faction models, example, forsaken humans use the new human model, high elves use the new blood elf models, also to make them look a bit different from regular night elves, the highbourne could use a night elf'd version of the blood elf model. i.e. it's the blood elf model and animations, but made night elf height (nor change in stature), night elf features like ears, glowy silver eyes (males will have silver eyes too), night elf hair colour and hair styles instead of blood elf ones, night elf purple skin tones too. This allows them to at least have a different look and feel while being night elf too.