When those boats bringing in almost all the ammo, spare parts and new rifles stops being quite so cheap, then where will the plentiful ammo and somewhat plentiful parts sources come from?
5.56 & 7.62 Nato looks good when you compare it to domestic x39 in both calibers.
There are enough domestic producers where parts and ammo arnt an issue and it costs about the same. The only reason 545 hasn't caught on with most domestic producers is because the surplus is so cheap there's not enough profit margin. Once the surplus dry's up there would be an open market and a strong demand for producers to fill the void.
According to that page you posted a link of it estimated the life of an AK for only 40 years but they are still finding AK's from the first production run (1948-1951) in combat zones in Africa and the middle east that are still being used. That's a little more than 40 years
As a personal preference, I like the 7.62 X 39 round far more than the 5.56mm. Although the chart shows the "range" of the AR VS the AK, our army boys are picking up AK's and using them due to the fact the AK will penetrate at a few hundred yards and the AR won't!
Looking at the plastic features of the AR, and the reliability built into the AK design, I personally believe the AK will outlast the AR by several years. Don't really understand where the people that built the chart believe otherwise. (I always believe what the internet says- NOT).
To me effective range should be the range at which a bullet does the job intended - not the distance where it will print on a paper target. I have a few SKS's, AK and LR-308. I did buy a couple of lowers for AR's, and will probably build at least one up into a rifle, but probably will build it into a 450 Bushmaster, 6.8 SPC, 458 Socom or similar. May build one up into 5.56 later - not sure. I do have a lot of high power military rifles - 6.5 X 55, 7.5 Swiss, 303, 8 mm, 7.62 X 54, 30-06 (Garands & US Enfield) and others. Also have .243, .308's and even a little M1 carbine (30 cal.)
I Just like a Rifle that can reach out and do what it is supposed to do every time!