If the Ukranian pipeline of cheap SKS's/Mosns/SVT-40s dries up, along with the ammo, then another of the former East Block countries will step in to fill the gap.
I don't doubt WestRifle's expertise in the area, or that the majority of the current supply is coming out of Ukraine (whether out of Ukraine's own stockpiles, or through being funnelled through the Ukraine by other nations), but I have my doubts that if the door closes on the Ukraine supply, that another will not open up somewhere else.
There is still far too vast a stockpile of those arms in the former East Block, and far too much $$ to be made shipping it to Western nations like Canada. You think we get them cheap here? We pay 4 to 8 times the going rate for old comblock surplus that most of Africa and the Middle East pays. The fact is that while $200 mosins and sks's, and $300 SVT's are an absolute bargain for the Canadian market, that kind of money buys AK-47s, plural, in most of the third world, where mosins and SKS's are pretty much "give-aways" as sweeteners for larger arms deals.
Someone, somewhere, in the former East Block, will re-direct the flow. There's just too much easy money at stake. Is there a risk of a temporary price bump? Sure. And sooner or later, the overall supply will dry up completely. But as it stands, there are still uncounted millions of of surplus arms in the former East Block. Most likely, another one of the East/West "straddle" states will become the new funnel (Czechoslovakia and Poland come to mind). To say nothing of the supply of Chinese SKS's making their way across the ocean (the supply bump there is from a shipping company getting skittish - not some fundamental trade reason - some other company will see the money to be made and fill the gap).
I'm not worried.
Mind you, I'm also not worried, partly because I already have a good example of each of SKS, SVT, and Mosin. So even if the supply does mysteriously vanish, I'm ok, I don't need a stockpile.
And there will always be a steady flow of milsurp arms throughout the world. Always has been, always will be. If you ever want to see an early example of milsurps coming to Canada, look up the sordid history of how hundreds of thousands of French Chassepot rifles, captured by the Prussians in the Franco Prussian war, were funnelled by the Prussian Government through British arms merchants and then out to the colonies and Africa.
SKS's, Mosins, SVT's dry up? Take a deep breath, hold onto your wallet, and wait for the next "big deal" in milsurp to come along.