Yah, I think it's safe to say Sanchez is untouchable. Kingery and Crawford are not.
It's rare teams get somebody's top prospect in these deals anyway. Let alone a Top 10 leaguewide guy. Certainly not for a rental. That's what they ask for, that's what writers write about, and then in the end it's other guys. If memory serves Thompson and Williams were both the second-choice guys from Texas. Verlander got the Astros' 3rd, 9th and 11th at the time (according to MLB). But he was controllable. If you're only get Machado for 3 months I don't think you give up more than two decent pieces (though Lively is just a throw-in in the above proposal really).
Can you do a PTBNL or cash component to the trade that's contingent on him re-signing?
Unless the O's want to dump the $ or a rival team is aggressive, it's still early to worry about it. If this team is playing ..550-.600 baseball on July 15 this conversation is gonna be a lot simpler. Ditto if they're under .500.