I have read the previous posts and do not disagree with them, but I'm going to answer in somewhat of a different vein.
The difference is I would suggest you think not about trading in a first rifle to buy a second rifle but instead, keep the first rifle AND buy the second rifle! The .30-06 is such an all-around rifle, its ammunition availability in different brands and bullet configurations, it is a no-brainer to always have one of these. It can serve as your back-up rifle on out-of-state hunting trips (you really ought to take a back-up on such trips because if something happens to your only rifle . . . then how much time, effort, money are down the tubes because your one tool is out of commission?).
But feel free to keep the .30-06 and buy a .300 Winchester magnum. Of, if it were me, to keep the .30-06 and take a bigger step up to the .338 Winchester Magnum. If you want to hunt whitetail deer and pronghorn antelope, it might make sense to keep the .30-06 and buy a .25-06, which is great for deer and pronghorn.
I use the .30-06 to kill elk, and it has not let me down so far on the three elk I have killed. It hasn't let down my hunting partners who have taken many more elk than I have, also with the .30-06.