[They could just spend the rest of the journey in silence with the awkward and lustful air. They could not think about it But Soundwave feels he ought to say it. Get the bad or uncomfortable stuff out of the way, so they can just focus on the good for the rest of the day. Hopefully, for several more days.]

I can't keep my first promise to you anymore, but... Promise you'll wait for me.

[He stops and turns to face her fully, visor meeting with her emerald.]

No matter how long I may be gone, wait for me. I'll come back to see you.

[He won't know if he'll disappear again this time, or how long he'll disappear for. One week? One month? More than two months? No, he can't predict the future at all. But, weirdly enough there's confidence in his voice- confident that he'll find his way back to Monika.]