By 2019 we'll probably be stuck on 14nm. Power consumption is the main factor at play here, and its returns are diminishing with every manufacturing process shrink. That kind of computing power would require something at least comparable to the original PS3 / X360 in terms of casing, PSU and cooling - huge and expensive machines, a business model Sony and MS are not likely to return to.
Besides, the RAM increase will be smaller. The only reason RAM increased so much this gen is because consoles traditionally lagged way behind the average PC (the GC for instance was like 27 MB when a PC would push 128-256 MB) and needed to catch up due to OS, more complex features and whatnot. Expect a four times increase, maybe six times if consoles take longer to release and we're lucky.
Anyways, it's way too early. Too many variables. We don't even know if Sony is going to release a new console, or if it'll even be around in seven years, or if it'll opt to follow the business-as-usual scenario instead of pulling a Wii...
