I don't speak Swedish natively, but I think it's because "will be" translates better as "kommer att vara" or "ska vara". "Blir" emphasizes the change, so it's more like "become"/"is becoming". Also note that "will be" is in the future tense, while the Swedish sentence here is in the present tense
If everyone at home wakes up at midnight during the midnight sun, should one say "God dag" or "God natt"?
It's worth to mention that "God natt" is actually not used as a greeting or farewell phrase in Swedish as it is in English. "God natt" is said just before going to bed really. It's almost a synonym to "sov gott" (sleep tight), but you could say it to someone who were still staying awake as you went to bed which you wouldn't do with "sov gott".
So if someone goes partying on saturday night, should I tell him "god kväll" or something?
You could say Ha en trevlig kväll! – and you probably wouldn't say Ha en trevlig natt! unless you really want to stress that you expect him to be out until morning.
This was once the same, at least in American English, but it shifted within the last 100 years or so. Living languages keep changing like that.
Is there an issue with how the voice pronounces "igen" here, or is that how it is pronounced following an "a" sound?