The DC Comics website have officially confirmed this, guys.:
Life in Central City can be pretty fast paced, but something tells us that won't be a problem for its newest resident...
You know the old saying: When life hands you lemons... you're going to need some help from another fellow speedster!
Preferably Wally West. Obviously.
WALLY WEST IS FINALLY HERE!
And just incase you haven't noticed already, it's most likely to be the Wally West from a different universe (Earth 2), who is African-American. Both Warner Bros and the CW have confirmed that Keiyan Lonsdale will be playing the iconic role of Wally West from a different universe in the new season.
While news of Wally’s arrival on the show will undoubtedly please fans, it’s not altogether surprising. When both Iris and Joe West were announced for season one, it seemed pretty likely that eventually Wally would join the fold should the show prove successful. - dccomics.com
Lonsdale was actually most recently seen in the 2nd installment of the Divergent series. He is a growing actor, and this role given to him will surely make him alot more well known!
Executive producer Greg Berlanti reiterated the fact that the change in ethnicity was the plan from the beginning: 'We made the West characters African American so we can eventually head in that direction, absolutely… That’s our hope.” - screenrant.com
WHO IS THE ALTERNATE WALLY WEST?
The alternate version of Wally West, who is african american, is the Kid Flash of another world (The New 52). As a 12 year old, he was caught by Barry Spray spray painting on a wall and removing the Flash symbol.He shares a relationship with Iris West as her nephew.
Five years later Wally learns the Flash's identity when he encounters the future Flash who reveals himself to be Barry Allen 15 years later from the current timeline. However after learning the goals of the future Flash he absorbs a part of the speed force during an explosion while Barry of the present timeline fights the future Flash turning Wally into the new speedster. - comicvine.com