What to text when he says we should definitely make plans soon though

This phrasing is classic non-committal language. He's not saying 'I want to see you Wednesday at 7.' He's saying something vague that sounds nice but costs him nothing. People do this when they like someone but aren't ready to invest effort yet, or when they're testing the water before committing to a plan.

Here's what matters: this is not a rejection. It's a soft yes. He's leaving the door open. Your job is to see if he'll walk through it. If you respond by being equally vague, you both stay in this floating state indefinitely. If you respond by suggesting something concrete, you'll quickly learn whether his interest includes follow-through.

A good reply proposes a real plan. Not a vague idea, but an actual activity with a timeframe. Coffee Tuesday. Drinks this Friday. A walk Sunday afternoon. Something he can picture and say yes or no to without doing mental work.

This accomplishes two things. First, it shows you're interested and willing to make it happen. Second, it puts the ball in his court in a way that requires an actual answer. He can't hide behind 'soon' anymore. If he wants to see you, he'll engage with the specific thing. If he doesn't, his silence or deflection will tell you he was just being polite when he said 'definitely.'

Send your reply and give him two days to respond. Not three hours. Not a week. Two business days is a fair window to see if he's interested or just leaving a placeholder.

If he responds with his own suggestion or confirms yours, move forward. If he ignores it or says 'let me get back to you,' he's already showing you how he prioritizes you. It's okay to follow up once after 48 hours with something like 'let me know what works.' After that second attempt, stop. You've given him two clear openings to step up. Anything beyond that is chasing. People who want to see you make space in their calendar.