In WW2, substantial numbers of Soviet citizens worked with the invading German army. Ukrainians, most notably, were ambivalent toward the Nazi occupation because of anger at the Soviet government.
However, Nazi racial theory suggested that such peoples were sub-human and ought to be slaughtered en masse. While plans for systematic Slavic extermination were never put into action to the same degree as the Jewish Holocaust, millions of Slavic civilians were still killed.
Did the Nazis plan to eventually murder the hundreds of thousands of Slavs who sided with them over the Soviet government?
I think you are misunderstanding the nazi view of their (for lack of a better word) sub-humanness.The Nazi's saw three options for subhumans: slavery, displacement, or death. The Nazi's also ranked humans and subhumans into further orders(French and Italians being superior to Celts who themselves were superior to Slavs etc.) This is part of the reason Slavic peoples were far more likely to be sent to concentration camps rather than the extermination camps.
OK now to answer your question....
Did they plan to murder them? No. Did they plan to enslave them? Absolutely. As far as the Nazi's were concerned they were the wise Slavs who recognized the Aryan's as their superiors and masters. The Eastern Masterplan was very clear on this under the principle of Lebensraum ("living space" for the German people) The Nazi end goal was to establish an agricultural empire stretching across all of eastern Europe. They envisioned the structure of this new society as not dissimilar to the Antebellum South in the US, Germanic masters overseeing vast slave plantations of Slavs. They hoped to then out breed the Slavs (through both German fertilization and Slavic sterilization programs) and overtime wipe them off the face of the earth as well. But that was to take place over generations. In the Nazi's minds the Slavs were fighting for their own enslavement recognizing their Aryan masters. This was especially the case of your example of Ukrainians which the Nazis saw as an ideal breadbasket. To the Nazis the Ukrainian ideas of an independent Ukraine were useful to exploit but never going to happen...they wanted Ukraine and Poland's fertile land more than anywhere else. Those Ukrainians would have become field slaves on Nazi grain plantations.
Edit sources
Bloodlands: Europe Between Hitler and Stalin Timothy Snyder 2010
The Ideological Origins of Nazi Imperialism by Woodruff D. Smith 1986