Quite possible, but in that timeframe, it would be hard for a (presumably) Labour Government to transition from closer cooperation on veterinary checks (its likely manifesto position) to re-entry to the single market, let alone rejoining the Union proper.
It's interesting that you raise the point of Ukraine. When it prevails, which God willing it must, then the EU will likely have to fast-track its entry into the Union, a decision that will have immediate economic consequences for the other Member States. If a British Government was ever serious about rejoining, then that moment might be opportune, and it might find the other countries in a less retributive mood.