Has AMD said that the 5700XT is a 4k card? Last I looked, all their demonstrations and benchmarks were at 1440p. As for being "watered-down architecture" - care to expand on that? Are you referring to the rumor that Navi 10 keeps some GCN elements? If so, which? The parts that matter are brand new, and the biggest (on-paper) update since GCN was introduced. If it keeps a few non-essential parts around to shorten development time, who cares? Also, you seem to think Navi 10 is going into a console - it isn't. The next-gen Xbox and PS will be Navi-based, but that's the architecture Navi, not the chip Navi 10. We have no idea about the CU count, VRAM amount/bandwidth, or anything else.
As for 4k on consoles, the Xbox One X does native 4k30 in quite a few games (no, not scaled, but a lot of other games do upscaled 1500-1800p at 30fps or higher, which still looks far better than 1080p), and some esports titles even do native 4k60. On hardware that's essentially an RX 480. Does the level of detail match Ultra settings on PC? Not necessarily, no. Does it matter? Not really. It's a great gaming experience for a relatively low cost, and a lot easier to get into than PC gaming. PC gamers really ought to be thankful to the console industry for recruiting more people to their interests, not whining about how the hardware is inferior.