I'm reading this change a bit differently to you guys I think.

This is how I see the change given my current situation:

I currently don't rated BG so don't have a rating at all. At 1750 5v5 rating I get a cap of 1880 or so. I am allowed to do arena to achieve that full allocation of 1880 as far as I see it.

The 2/3 calculation comes into it if I had a BG rating of 1750 also. In this case my CP cap would be 1500 + (1880-1500)/0.67=2070. In this case I can only use arena wins to hit my arena cap of 1880 and need to use Rated BG wins or daily/holiday normal BGs to make up the 190 difference.

For anybody with <1500 rating in either the change is simply that your total cap for either will be 1500 rather than 1343. Unless the cost of pieces goes up this seems to be an overall buff to lower teams. Either way I achieved full vicious about a month ago now and have a useless stash of CP which I am just using to collect different looking weapons. WTB conversion of CP to VP IMO