A very interesting article posted by jmauser concerning - SKD Trials Article:Yuschenko/M9130.info
There has been in question of the transition from spike to blade in this post. In the last paragraph of article, it answers that question. Now production of transition would be dependent on spikes in stock.
Below is a copy of last paragraph of article. The whole article is well worth reading.
However, at that moment there was no adopted knife blade bayonet for the SKS. Production started according to existing drawings which contained a spike bayonet. Four days after the adoption of the SKS, the Simonov design bureau (OKB-19) and factory No. 536 design bureau submitted their knife blade bayonet designs for adoption, but neither of them were accepted. A new bayonet design was created according to the advice of the group of Marshal of the Soviet Union veterans, it was accepted on November 2nd, 1949. Leftover spike blade bayonets were supposed to be used in production within the next 3 months, afterwards, production was supposed to be switched to the knife-blade bayonet.