Dave Raymond will be doing play-by-play work on 45 Rangers television broadcasts and 12 Rangers radio broadcasts in 2016, per Barry Horn on Twitter.
Raymond has done quite a bit of minor league and major league play-by-play work, and did work on the Houston Astros radio broadcasts from 2006-12. More recently, he's done work on the Longhorn Network, and has done basketball broadcasts.
There's been talk previously that Tom Grieve would be doing less broadcast work going forward, and the assumption has been that Mark McLemore would take a bigger role -- however, this would seem to indicate that Raymond is going to be doing that, instead.
I don't really have an opinion on Raymond one way or the other, although the fact that he has extensive work doing baseball play by play seems to indicate that, after the John Rhadigan and Dave Barnett hires, the Rangers have figured out asking someone to do this for the first time at this level doesn't really work.