Ответ:
1. It's hot. I'll go for a swim.- an on-the-spot decision.
2. Outdoor activities will soon be replaced by online games.-a future prediction based on what we think will happen.
3. Be careful! You're going to cut yourself with that knife.- a future prediction based on what we see.
4. Paintballing is becoming very popular with teenagers.- a gradually developing situation.
5. Aidar is starting a new hobby this weekend.-a fixed arrangement in the near future.
6. Now that I have the time, I'm going to leari how to paint.- a future plan or intention.
7. Surfing lessons start at 9:00 am.- a timetable.
8. I'll come see you play rugby today, I promise. - a promise