If Germany retains the Ukraine as a client state, it is likely that a lot farmers in Eastern Germany will be put out of business due to German markets being flooded with cheap Ukrainian grains. So I would guess that agriculture in the region would not just stagnate, but decline as a whole. As for industry moving there, I find it unlikely as it is not an ideal location. IFAIK, industrial regions are where they are because there is usually a resource nearby, like iron or coal. I don't know a ton about industry though, so I could be wrong. The remaining farms would probably mechanize, most likely with government support, so as to keep a good amount of Germans in the region and prevent it from being "Polonized".