I said one or two days ago the same concern - before Medvedev. I think that scenario is real. The Russians cannot give up the Crimean. The loss of face in their view would be too big. In mine and ours, too.
Its the Crimean. Its Sewastopol. Its tradition, history, nationalistic narration, sentimentality, dreams of a glorious past - its all that and then more. Its Putin, and Putin always escalates, cannot accept to be seen as weak, must slam fists on table and stomp with his feet. Macho worldview. Men are tough and strong. Russians are invincible. Boys dont cry.
I think if there is a realistic chance for an offensive against Crimea, they should go for it. But not without being properly prepared to retaliate in case of the Russians then runnign total amok. I bet 3:1 they would. Crimea is a red rag for them.
Better maybe to destroy Kerch bridge, establish an air traffic denial zone via SAMs and and anti-ship missile screen in the Asow sea, retake the Southern coast of Ukraine to the Black sea, and then cut the water supply from the North (Ukraine) to the South (Crimea). Maybe not clever to attack the Crimean peninsula head on. Let Russia choke on it while Crimea gets stuck in its gullet.
But first Ukraine must get there, and win the rest of the war first. I dont take it for granted they can. Its open. Time is on Russia's side.