This is a list of features announced or mentioned by the developers to possibly come to ARK: Survival Evolved.  Due to the shifting nature of development, there is no guarantee they'll be implemented. 

Items

Gaslight lanterns [1]

Indoor lighting [2]

Some light tier between standing torch/lamppost [2]

Flashlight [3]

Reinforced Stone Box [4]

Tek Tier [5] Surveillance equipment [6] Cloaking Devices [5] Multi-HUD Visor (magnifying glass for the distance, maybe with more stat-infos) [7]

Wall banners (Flags hanging from walls) [8]

Heat vision [9]

Shotgun beanbag ammo [10]

Warhorn [4]

Electrical Keyboard [11]

Xylophone[12]

Weapons

Armor / Clothing

Dinosaur armor [9] Dino mounted cannons for primitive [12]

The ability to add armor to the Training Dummy[15]

Structures

Half-walls [1]

Colorization pass on older structures [10]

Flipping Sloped Walls Upside Down [12]

Wall mounted coel for base decoration [16]

Dynamic-Length Bridges (first announced for v245 but then deferred)

Consumables

Bread and Jam [9]

Laxatives [17]

Coffee[16]

Vehicles

Environment

More underwater harvestables [16]

More seeds, and making seeds only appear in certain biomes[6]

Map

Additional caverns and biome development for The Center [13]

Sunken Obelisk with underwater boss[16]

Weather

Hail and other weather cycles [1]

Maybe a rough sea[4]

Game mechanics

Mechanized transportation system [10]

Potential airships/airship bases [10]

Naming items [18]

Carrying weapon and torch together [13]

Tribe-leveling [9]

Alliance rankings/privileges [13]

Localized injuries and bleeding (and bandages) [19]

Hold breath while in scope function [17]

Ability to stop babies from growing(Tek Tier) [17]

Craft from remote-inventories (i.e. using resources of a storagebox directly instead of transfer them first) [20]

Auto Flight/Run key [21]

More creature tracking options [22]

Use of map/GPS while mounted on water creatures[22]

Behavior

Carnivores more active at dusk and dawn [2]

A fix to Pteranodon's spazzy nature [2]

The Carbonemys will have the ability to retract into their shells [6]

Possible sibling boost [17]

Alarm Trap can cycle aggression on nearby dinos [17]

Possible breeding stat [16]

Dino support of arbitrary gear[22]

Scope

Roaring feature for all dinosaurs [2]

Sound pass[23]

Appearance

Footprints [9]

Different sounds for walking on different surfaces[6]

Creatures

For specific creatures see the section of Unreleased Creatures at the Dossiers. 

UI

A skittish command for creatures [6]

Improved server browser [10]

Separate use key while mounted[22]

Other

ARK: Primal Survival

Disc Edition available after release[23]

References

[1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25]