I dunno about traits like color ever going back to the hues we see on pure russian/eurasian wild stocks...
But the physical structure ricky refers to are the ones needed to live feral or live barned...
Feral hogs need a long snout for deeper easier rooting and a taper that makes them able to slice thru the cover at full run.
They need ground clearance too. They need little fat so they get long legged and lean.
Barn yard swine develop to suit their needs too... Short snout and big wide head takes more space at the feed trough limiting competition.
Shorter legs and broad shoulders also make working the feed trough easier too.
But in the end the DNA will be a mix of the breeds in that feral hog... His offspring cannot ever "develop" russian DNA but with enuff crossing to a pure herd could water down the feral domestic DNA soon enuff.
These hogs are blends of any and/or all domestic breeds... Spanish little black hogs, bright red Durocs, belted Hampshire (bred for thin skin), pink Yorkshires and others are all in the mix so not likely they would acquire DNA they do not already possess.
Brent