Darkmaste is right. All polaris gpus are RX 400. I'm not sure what gpus you are referring to @Molhel. The link you provided didn't clear anything up either as it was for the older r7 300 series(2015). There are r7 400 cards but they are all re branded gcn1 and gcn2 cards and they are all OEM only. A deceitful practice AMD has done for years to help OEMs, Dell HP ETC, market old products as new. But I digress. I haven't heard of any new r7 cards coming out but I wouldn't be surprised to see some OEM R7s with the vega numbering system when the time comes.
EDIT: To be fair, before someone calls me out on it, Nvida has done much the same with their low end cards. However, they seemed to have mostly stopped it with the 900 series. A trend I hope continues.
I just meant that there are new and old R7, 200, 300, 400, doesn't matter, and that we couldn't know what he had just by "R7" card.