I don't get too excited anymore when I hear the military is considering a new round. The 6.8mm SPC was going to fix many of the problems, but never really got off the ground. The 45acp was going to make a come back, but who knows. Maybe the 338 will have better luck getting into service and staying there, but military doesn't change it's mind on calibers very often.
The 6.8SPC is dying out because of politics; the SF guys that developed it went "off the reservation" and didn't go through proper channels. That means that the usual suspects didn't get any bribes, and no one managed to land a "cost plus" contract that could be milked for huge money.
The .338 Lapua is the logical choice as it has already got a proven track record. It's being used by the IDF in a sniper system made by HS Precision. No doubt a whole bunch of eyes are watching how that goes.
Xtreme Engineering got a solicitation for a Corps wide contract recently.
338 Lapua is great but couple other ones coming in that might give it a run, such as the 338 Norma (standard mag box with 300 SMKs at 2800+) and the 338 Xtreme for sure. I was highly impressed with their systems and so was the USMC when they shot it at Quantico a couple months ago.
BH