I'll give a disappointing answer which is that i don't know and i don't think anyone really knows right now.
The only two things i am sure of is that Russia will win and that it will not renounce the regions it has already annexed. Beyond that i don't know what will happen, and as for the intentions of the Kremlin i think several possibilities are still being kept open and which exactly of these they will choose will depend on how things continue to develop and how Ukraine and the West behave...that is whether they accept Russia's terms or not. If they refuse then Russia will have to go further and take more. How much more exactly and what will become of the rest of Ukraine i won't speculate on because too many factors are at play that are still unknown.
But i will say this about the topic of annexations: i think the best solution is not annexation but a restoration of a union of Russia, Belarus and Ukraine (that is a territorially reduced Ukraine because even in this scenario it is not getting the eastern territories back...the people there simply would never agree to it), but i also don't think that is going to happen under a bourgeois Russian government (though if the KPRF come to power after Putin retires we may see them eventually make a push in this direction).