It's interesting how casually we replace concern for the population with concern for the political entity. No, the Ukrainian identity will not cease to exist with the replacement of the political entity.
What Russia has done in the past is take people who want to hold onto their old national identity and send them to labor camps far away where most will die, and migrate Russians to the areas so as generations go by Ukrainian identity would be fully gone.
Do you have a source for this? The closest thing I've heard of was vague reports of children being shipped to Russia. I'm not denying it has ever happened, but the question is what is the motivation, how systematic is it, etc.
Ask Ukrainians what they think about that. Putin made it more than clear that he wants to erase the Ukrainian identity. [1] In this case, the political entity of Ukraine represents the Ukrainian population, which wants to be free, democratic, Europe-oriented, and last but not least, never ever be under Russian dictatorship again.
Russias attitude towards Ukraine has turned borderline genocidal since the start of this war.