He used to talk about the future, now he avoids it: what to do

A single vague reply is weak data. People deflect plans for all kinds of reasons, including work stress, family stuff, not wanting to jinx something, or simply not having thought about it that day. What matters is the shape of the change. Did he used to bring up plans unprompted, and now only answers when you ask? Did the specifics fade, like a trip with dates turning into a vague "someday"? Did his other warmth stay the same or cool too? If he's still affectionate, texting you about his day and making time to see you, the avoidance may be about pressure or uncertainty in his own life. If the warmth is thinning along with the future talk, take that more seriously. Notice also whether he gets noticeably uncomfortable or changes the subject quickly when plans come up, versus just being neutral about it. Discomfort points to something he's carrying. Neutrality points to him not thinking about it much.

Whatever you say should do three things. It should show you noticed, without accusing him of anything. It should make clear that you're okay talking about it, so he doesn't feel like he has to manage your reaction. And it should ask an open question he can answer honestly, without forcing a yes or no about the relationship. Something in that territory works better than asking "are we still going to do X." Keep it short and specific to what actually changed, like the trip or the move or the meeting his friends that he mentioned before. Then stop. Don't follow it with three more questions or a long paragraph explaining how it made you feel. The point of the message is to open a real answer, so let him have room to give one. If he replies with something warm and specific, you have your answer about the pattern. If he replies with a brush-off, that's also information, and you can respond to that directly instead of guessing.

Timing matters more than wording here. Bring it up when you're both reasonably rested and not in the middle of something stressful, usually in the daytime or early evening, not after a few drinks or late at night when small things feel large. If you bring it up and he takes a few hours to answer, that's normal, and it doesn't mean the conversation failed. Give him a day before you read anything into a slow reply. If he doesn't respond at all after a couple of days, send one short follow-up that's easy to answer, something like checking in about whether he's free to talk this week. Don't send a string of messages or a long "I need to know" text. If he still doesn't engage after that, you have your answer about how much he's willing to talk. Stop chasing the conversation, keep living your own life, and decide what you're going to do based on how he treats you when you're in the same room.