no im not wrong.
if durango runs only ddr3 than maybe. but it will be compensated by the ultra fast pool of esram as stated. both 360 and ps2 had the ultra fast ram and it enables them to keep up with systems with more bandwidth. 360 only has 22gb/s while ps3 has 48gb/s or so.
even ps2 which has much inferior gpu due to the time of its release, it had about 3.2gb/s while xbox has 6.4gb/s and it fought well though hampered by low res IQ. now imagine if ps2 had as good gpu as xbox but with 128mb of 3.2gb/s main ram, it would easily be the superior hardware. this looks like the case of ps4 vs durango.
in the end 8gb vs 4gb is a huge win for Durango developers and i also browse beyond3d, developers have stated more ram is better when the speed difference is not that great with esram in the picture. furthermore, 192gb/s is no big deal. my pc gpu has 300gb/s now and games like crysis2 still runs sluggish at certain points with only 1200p full settings.
the expectation of a more advanced mulit tasking OS seated in the background will suck a portion of the 4GB.
so no, 4GB is not enough for PS4 to compete with Durango in the same price bracket. either Sony put another 2GB or they have to market PS4 as a mid range between Wii U and Durango.