Taking into consideration all different factors, I've compiled a list of all those likely to receive a cross-generation evolution. I'm personally quite sure we WILL be getting some in Gen VIII.

Practically Guaranteed:
>Magcargo
>Corsola
>Chimecho
>Eevee
>Lumineon
>Qwilfish

Likely:
>Komala
>Dewgong
>Farfetch'd
>Maractus
>Carnivine
>Stantler
>Girafarig

Vaguely Likely:
>Primeape
>Kingler
>Salandit(Male)
>Torkoal
>Swalot
>Whiscash
>Mr. Mime
>Jynx
>Lanturn
>Venomoth
>Arbok

They Are Gimmick-mons, and/or Their Sucky-ness is Intentional, So Who Knows:
>Luvdisc
>Delibird
>Spinda
>Dunsparce
>Kricketune
>Kecleon
>Chatot
>Sudowoodo
>Ledian & Ariados