Let me fly a kite here. I am not sure of this, so tell me what you think. In a previous post I argued that the "is Acts formative or normative" discussion is hermeneutically unhelpful. I think it is more nuanced than that and we shouldn't start by assuming that it isn't normative for reasons outside the Bible.
When the Holy Spirit came in Acts 2, Peter said it was the fulfilment of the Joel prophecy of God pouring His Spirit on all flesh. The purpose of the Spirit coming is power for world evangelisation (cf 1:8 and elsewhere). I take it that things like "your sons and daughters shall prophecy, your young men will see visions and your old men dream dreams" therefore is indicative of the work that the Spirit will do to further the gospel. Spiritual gifts and enduements of power for world evangelisation.
As far as I can see there are three visions from the Spirit in Acts, all for the sake of witness and world evangelisation: Stephen (for whom it is also glorious strengthening as he dies); Peter in Acts 10 seeing that God has accepted the Gentiles, allowing for gospel witness to them for the first time in Cornelius' house; and here with Paul where the consequence is to take the gospel to whole new spheres.
I previously argued that Luke tells Theophilus and us stuff not just for historical interest, but as indication of the way things are done. For example, how to set aside people when you hear the Spirit (in Acts 13 and Acts 16, so it wasn't a once off), or how to preach an evangelistic sermon to Jews (Pisidian Antioch, Acts 13). And now with the Macedonian vision we have one of the very few accounts of God actually doing what was promised in Acts 2. Do we conclude that, because there are few accounts, God acting like this is a one-off? In which case we don't expect him to do it today. Or do we read it as a main instructive example of a more universal principle given in Acts 2 (namely that because the Spirit has been poured on all flesh, people will see visions and dreams from the Spirit for world evangelisation)? In which case we may expect Him to do similar things today. Here are completely off-the-top-of-my-head thoughts:
1. It will turn on whether we think Acts as a whole is an outworking of Acts 2; and whether we think that it is a closed book that describes the events of the time or an open-ended book, the principles of which continue till the end of the Great Commission
2. Does Luke select his material in Acts as a whole to explain and illustrate the outworking of Acts 1-2? I think a case could be made for that, in which case we must relate everything in the whole of Acts back to God's purpose in giving the Spirit for world evangelisation
3. Paul, Silas and Timothy (and Luke) were not expecting the vision, but neither do they seem very surprised by it. If it were a dramatic one-off I suspect we might get a little more than the quite mundane in-passing note that Luke gives.
4. I like the way Luke puts it "Paul saw a vision, so we concluded." The group sat around, chatted about it (seemingly perfectly normally) and came to a collective decision of what to do. Note that the vision didn't tell them where to go or who to talk to. It is not an imperative, a command, or highly detailed. They act on it in the best way possible - "its a man from Macedonia, let's go to the chief city of Macedonia and see what happens" - but not with any divine certainties about what will come next. (I wonder if sometimes we need to be more relaxed about some claims of dreams and visions, not claiming too much detailed divine imperative for them, while feeling a freedom to act and explore on the basis of them?)
5. The temptation is to say "if Luke is giving us an example of a normal Acts 2 pattern, why don't we see more like it today?" but without the accompanying commitment to world evangelisation. We can argue the toss either way in theory, but I suspect we only get the right answer if we are actively involved in doing what the Spirit was given to do. Hence hearing many more accounts of supernatural activity from frontier pioneering missions than in comfortable suburbia. C.S. Lewis said "if you want to see trains go and live by the railway. If you don't want to live by the railway, don't argue trains don't exist."
6. Therefore I wonder if this is a case where it is impossible to know whether our exegesis is correct without living out the gospel. Without being active in the cause of world evangelisation.
I want to finish on a wider principle. I don't think there is any certainty in ANY exegesis unless we are living out the gospel. God has a habit of revealing himself to those who don't just think about Him and talk about Him but who do what He says. Sitting in the study trying to answer the question in a purely theoretical, abstract way is probably never what God intended us to do with the Macedonian vision. I suspect we are meant to hear about it, and long for Joel-type visions and dreams as God stirs in us a passion desire to do the work of the gospel in fresh fields.