The 7mm-08 and .308 are essentially duplicates of each other. So there is really no point in having both until you get all your bases covered then start filling in the spaces with wants instead of needs.

IMO the spacing should go something like this.

.22lr
.22 centerfire (.223)
something in the standard 25 to 30 caliber range. (.270, .280, 30-06)
.338 of some sort (.338 Win mag, .338RUM)
dangerous game cartridge of some sort. (416 Rigby, 458 Lott, etc...)

If you want to keep in in the short action family then...
.243
.308 or 7mm-08
.338 Federal